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what is electricity? part 3: capacitors, dielectrics and confusion

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an electrophorus, apparently

Canto: I’ve found a useful website on the history of the capacitor, which tells us that the term condenser was an early term for a capacitor, presumably because it accumulates charge, condensing it – like condensed milk?

Jacinta: Condensation in chemistry, or whatever, means transformation from a gas, or vapour, to a liquid. Remember they were thinking of an electrical fluid in the early days.

Canto: Well this excellent website on the early days tells me that the effect they were creating by rubbing  a glass globe is now called the triboelectric effect. And by the way it was Franklin who worked out that it was the glass that was creating the effect – nout to do with water, it seems.

Jacinta: Yes, it’s an everyday effect – you can get it just through combing your hair, or rubbing a plastic pen on your sleeve and then picking up bits of paper. I did it at school! I was very sciencey in them days.

Canto: Interestingly, there are lots of nice comments on this website, pointing out that the term for capacitor in a number of European languages is kondensator, or variants thereof. But we get yet another story here on early Leyden jars, which I’ll need to unpick:

It was realized also at Leyden University that it worked only if the glass container was held in your hand and not if it was supported by an insulating material. Today we realize that the alcohol or water in contact with the glass was acting as one plate of the capacitor and the hand was acting as the other while the glass was the dielectric. The high voltage source was the friction machine and the hand and body provided a ground.

Jacinta: So sometimes water was used as a ‘plate’ instead of the tin foil on the inner surface, and the hand was acting as the other plate. So, different versions of Leyden jars. And the dielectric? Yet another unexplained term.

Canto: Yeah, they just never simplify things enough for fuckwits like us. A dielectric is apparently an insulator. Or, as Wikipedia expands it, it’s ‘an electrical insulator that can be polarised by an applied electric field’. Now, I thought that an insulator was the opposite of a conductor, that it tends to be a bad conductor, something that’s difficult for a charge to pass through. Or is that a resistor? Anyway, I can see how dielectric, meaning two, has to do with polarisation, positive and negative, but it still remains vague. I just thought an insulator kind of protects people from getting electric shocks.

Jacinta: So, going back to Crump, here’s a quote:

Franklin succeeded in giving Leyden jars both positive and negative charges, and showed that the force itself was stored in the glass of the jar with the charge being proportional to its surface area.

I DO NOT UNDERSTAND THIS. I WANT TO UNDERSTAND. Does he mean positive and negative charges at the same time? Is that what a dielectric is? And when he says the force was stored in the glass, and the charge bore a mathematical relation to the surface area of the glass, does he mean a different thing by force and charge? And if the charge is proportional to the surface area of the glass, does that mean that if the surface area of the glass was equal to, say, the surface area of a glassy planet Earth, you’d get a more than respectable charge? And if our universe has a surface area?

Canto: The universe isn’t made of glass, I learned that from Dava Sobel’s The glass universe. Or not.

Jacinta: Okay, let me look up some common definitions before we go on.

dielectric is a material that transmits electricity without conducting. That’s to say, an insulator (BUT I DON’T UNDERSTAND WHAT THIS MEANS). Examples of dielectric materials include glass, ceramics, metallic oxides, plastics and dry air.

An insulator, electrically speaking, is a material in which electricity can’t flow freely. In such materials, electrons are tightly bound – though it’s all relative. They’re said to be resistive. So presumably there’s a connection between resistors and insulators. Most insulators are non-metals.

conductor is a material that allows a flow of electrrical charge, aka a current. Metals, such as copper wire, are commonly used as conductors.

Electric charge – and I think this is really the biggie – is a state or property of matter when a certain force from an electromagnetic field is applied to it. Or when it is within an electromagnetic field. But we won’t try to define an electromagnetic field until part 30 or so. An electric charge can be positive (carried by protons) or negative (electrons). This is not, of course, a full definition.

Triboelectricity is a charge of electricity gained by friction. The triboelectric effect can be varied and unpredictable, depending on the precise structure of the materials being rubbed together.

A capacitor, originally called a condenser, a term first coined by Volta, is… well, we posted a piece over four years ago called ‘What are capacitors?’ – but we’ve never thought about them since…

Canto: Yes, I’ve skimmed through that piece and I barely understand it. Let’s just say for now that a capacitor is a device for temporarily storing electricity, but that it differs from a battery somehow.

Jacinta: Okay, one more term used in Hackaday’s ‘History of the capacitor’ that needs explaining is hygroscopic. It says that soda glass, whatever that is, is hygroscopic. Franklin used soda glass in his experiments, apparently.

Canto: Google only tells me something about soda-lime glass, which I’m hoping is the same thing. It’s the most prevalent type of glass, composed of 70% silicon dioxide, or silica, 15% soda (sodium dioxide) and 9% lime (calcium oxide). The other 6% is made up of ‘other’. Hygroscopic materials attract water molecules from the surrounding environment, either by absorption or adsorption, but Wikipedia, which gives a large list of hygroscopic materials, makes no mention of glass or silicon as hygroscopic, though it does mention sodium salts.

Jacinta: So let’s move on with the history of these electrical discoveries, and maybe we’ll solve the problem of our own ignorance along the way. I note that potted histories of the battery, such as the one I’m about to quote from, don’t bother to distinguish between a battery and a capacitor:

Ben Franklin built an electric battery using glass window panes and thin lead plates. Using his “electric battery,” a term he coined himself, he showed how electricity could be stored in the glass and passed through it. Shouldn’t we call it the great-grand-dad of electric batteries?

So let’s not worry about it, though I suspect Yank jingoism is at play here. Let’s move on to Alessandro Volta.

Canto: And the continuous current battery. Volta’s first contribution to electricity was to improve on the electrophorus…

Jacinta: And here’s a great definition of the electrophorus, a device actually named by Volta:

An electrophorus or electrophore is a simple manual capacitive electrostatic generator used to produce electrostatic charge via the process of electrostatic induction.

Canto: Clear as mud. An electrophorus apparently consists of a dielectric plate…

Jacinta: Yeah, something that transmits electricity without conducting it.

Canto: Okay, let’s clear that up – perhaps. Dielectric materials don’t have free electrons for conducting electricity – they’re insulators. Electrons are, of course, electrically charged particles, and in dielectrics they’re tightly bonded to their nuclei. What does happen when an electric field or current is applied is that they become polarised. This raises the question of what polarisation actually is, and what it is about an electric field/current that causes this polarisation.

Jacinta: Not to mention whether there is a difference between an electric field and an electric current.

Canto: Okay, more work to be done. There are different types of polarisation. The polarisation of light, for example, is a complex story which we’ll have to deal with in another 50,000 part series. But here’s a general description from Britannica:

polarization, property of certain electromagnetic radiations in which the direction and magnitude of the vibrating electric field are related in a specified way.

So, just off the top of my head, an electric current seems to imply direction, whereas electric field not so much. On electric polarisation, ScienceDirect, which takes material from scientific papers, has this:

Electric polarization refers to the separation of center of positive charge and the center of negative charge in a material. The separation can be caused by a sufficiently high-electric field.

I think this means that dielectrics can be separated in terms of overall positive and negative charge in their individual atomic make-up, so that they can become magnetised, sort of? Because I think of magnetism in terms of polarity. They can become polarised, like magnets, while not being able to conduct an electric charge. Maybe.

Canto: We seem to have come a long way from capacitors.

Jacinta: We got lost on electrophoruses. An electrophorus consists of a dielectric plate..

Canto: Okay, here’s another definition, from Oxford Reference:

An early form of electrostatic generator. It consists of a flat dielectric plate and a metal plate with an insulated handle. The dielectric plate is charged by friction and the metal plate is placed on it and momentarily earthed, which leaves the metal plate with an induced charge of opposite polarity to that of the dielectric plate. The process can be repeated until all of the original charge has leaked away.

Jacinta: So this gives me a visible image, of sorts. The flat dielectric plate – and I assume a plate is something flat and thin – is polarised by friction, and a metal plate, that’s to say a conductor, is brought into contact with it and then momentarily earthed (I DON”T UNDERSTAND THIS), which leaves an induced charge of opposite polarity on this other plate )I DON”T UNDERSTAND THIS EITHER), and with repetition the original charge is leaked away (DITTO).

Canto: It seems every explanation needs further explanation, and we’re constantly changing electricity’s tail. And we’ve only just begun 🎵.


History of the Capacitor – The Pioneering Years

what are capacitors?

Written by stewart henderson

December 12, 2021 at 12:34 pm

What is electricity? part 1 – static electricity, mostly

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'Ben Franklin acquiring electricity', filched, methinks, from Reddit

Canto: So it seems we’ve been here before but we’re back at the beginning again, because we’re still largely ignorant. And sadly, even if we finally get a handle on this complex phenomenon, we’ll be likely to forget it again through disuse, and then we’ll die.

Jacinta: So let me begin as naively as possible. Electricity is this energy source, or comes from this energy source, which travels through a wire by some kind of force that excites the electrons in the wire, which then oscillate and create an energy transfer along the wire, to a connector to a light bulb or a toaster, and when a switch connects the wire to the toaster it heats up your bread. But electricity doesn’t have to travel though a wire because I think lightning is electricity, but it needs a conducting material, which in the case of lightning is probably water vapour. I’ve heard somewhere that water is quite a good conductor of electricity.

Canto: Well, all that may or may not be true but what is voltage, what is current and why are certain materials conductors, and superconductors, electrically speaking, and what is an electric field? And I’ve heard that electrons really do flow in a wire, rather than just oscillating, though I’ve no idea what to make of that. 

Jacinta: My next step is to look for experts, and to try to put their explanations into my own words, for ownership purposes. So I went to the ‘expert site’, Quora, and found quite a few contradictory or confusing responses, but assuming that the response that comes up first is some kind of popularly selected ‘best’ response, I’ll focus on Anthony Yeh’s answer. Oh by the way, the question is something like ‘what do electrons actually do in an electrical circuit?’ – though even that requires prior knowledge of what an electrical circuit actually is. 

Canto: So let’s see if we can bed down the concept of an electrical circuit. So a website called ‘all about circuits’ gives us the basics, starting with static electricity. This was probably woman’s first discovery relating to the electrickery thing. Two different materials rubbed together – glass and silk, wax and wool – created this stickiness, this attraction to each other. And then it was noticed that, after the rubbing, the identical materials, such as two glass rods, exerted a force against each other. And another observation was that the wax, after rubbing with the wool, and the rod after rubbing with the silk, attracted each other.

Jacinta: Yes, this must’ve seemed quite bizarre to first discoverers. And they found that it worked as a sort of law. If the item was attracted by glass it would be repelled by wax – that’s to say, two rubbed wax cloths would always repel each other, as would the two rubbed glass rods. Which led to speculation about what was going on. The materials didn’t appear to be altered in any way. But they behaved differently after rubbing. Seemed like some invisible, quasi-magic force was in operation. 

Canto: One of the earliest speculators that we know about was Charles du Fay (1698-1739). Note the dates – we’re really into the period inspired by Galileo, Newton and Huygens, the early days of theoretical and experimental physics. He separated the force involved into two, which he called vitreous and resinous. They were at first thought to be caused by invisible attractive and repulsive fluids. They later came to be known as positive and negative charges. 

Jacinta: But when Benjamin Franklin (1706-90) came to experiment with what became known as electricity, it was still thought of as a fluid…

Canto: But hang on – this static electricity stuff must go back way earlier. Sparks fly, and you feel the energy on your skin when you remove, say, a piece of nylon clothing. And you see the sparks in the dark. I get it from metal door-handles quite regularly, and you can actually see it – it ain’t no fluid. Surely they noticed this way more than a couple of hundred years ago. 

Jacinta: Okay let’s go back thousands of years, to Thales of Miletus, about 600 BCE. I’m using Quora again here. He noticed that rubbed amber was able to attract stuff, like leaves and other ground debris. Theophrastus, a student of Plato and Aristotle, who took over Aristotle’s Lyceum, also left some notes on this phenomenon, but this didn’t get any further than observation. William Gilbert (1544-1603), a much under-rated genius whom I read about in Thomas Crump’s  A brief history of science, wrote a treatise, On the magnet, which compared the attractive, magnetic properties of lodestones with the properties of rubbed amber. He called this property ‘electric’, after elektron, the Greek word for amber. He also built the first electroscope, a simple needle that pivots toward an electrically charged body. Gilbert was able to distinguish between a magnet, which always remained a magnet, that’s to say, an attracter of metals, and an electrically charged material, which could easily lose its charge. So we’re now into the 17th century, and very far from understanding the phenomenon. The first electrical machine was constructed by Otto von Guericke (1602-86), another interesting polymath, in 1660. It was a rotating globe of sulphur, which attracted light material, creating sparks. Nothing new of course, but a useful public demonstration model.

Canto: So we’re now getting to a period when a few enlightened folks were set to wondering. And this was when they must’ve noted the phenomenon’s small-scale similarity to lightning.

Jacinta: Yes, and so experiments with lightning were undertaken in the eighteenth century, generally with disastrous results. The fact is, though Ben Franklin did do some experimentation with kites and lightning, he mainly focused on glass and amber rods. He noted, as before, that there were two different forces, or charges, attractive and repulsive. When a rubbed amber rod was brought toward another rubbed amber rod they repulsed each other. When the same amber rod was brought toward a glass rod, they were attracted. He considered there were two opposite aspects of the same fluid (for some reason investigators – at least some of them – was still thinking in terms of fluids). The identical aspects of the fluid repelled, while the opposite aspects attracted. He decided, apparently quite arbitrarily, to name one (glass) positive, the other (amber) negative. And we’ve been stuck with this designation ever since..

Canto: Yes, I’ve heard that it would have been much better to name them the other way round, but I’ve no idea why. And also, why is all this called static electricity? Obviously that name came later, but what does it mean? We hear people saying ‘I’m getting a lot of static’, which seems to mean some kind of interference with a signal, but I’ve no idea why it’s called that. 

Jacinta: Oh shite, we’ll never get to the bottom of all this. Here’s a Wikipedia definition, which might help:

Static electricity is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge. Static electricity is named in contrast with current electricity, which flows through wires or other conductors and transmits energy

Canto: Okay, that helps. Static electricity ‘remains’ – it has to be discharged. So lightning is a discharge of static electricity? 

Jacinta: I believe so, and that spark you get from the car doorhandle is a discharge of the static electricity built up in your body. Now let’s return to the online textbook ‘All about Circuits’. It points out that Ben Franklin did have a reason for his positive-negative designation. Here’s a quote: 

Following Franklin’s speculation of the wool rubbing something off of the wax, the type of charge that was associated with rubbed wax became known as “negative” (because it was supposed to have a deficiency of fluid) while the type of charge associated with the rubbing wool became known as “positive” (because it was supposed to have an excess of fluid). Little did he know that his innocent conjecture would cause much confusion for students of electricity in the future!

Canto: Okay, I’m not sure whether this is a headfuck. When wax is rubbed with wool they attract each other. Franklin thought in terms of fluids, and he conjectured that, in the rubbing, the wool removed fluid from the wax – so wool had an excess of the fluid, and wax had a deficiency. The deficiency, which of course wasn’t really a deficiency, he termed ‘negative’ and the excess was ‘positive’. Sort of makes sense. Though why people since have felt this is the wrong way round, I don’t get at this stage. 

Jacinta: So now we come to Charles-Augustin de Coulomb (1736-1806), and I suspect we’ll be dwelling on him for a while, because ‘All about circuits’ deals with him rather cursorily, methinks. It tells us that Coulomb experimented with electricity in the 1780s using a ‘torsional balance’ (wtf?) to measure the force generated between two electrically charged objects. 

Canto: Exquisitely meaningless at this stage. Anyway, onward and downward…


Thomas Crump, A brief history of science, 2001

Written by stewart henderson

November 28, 2021 at 8:52 pm

more on fuel cells and electrolysers

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Cross section of a PEMEL(polymer exchange membrane electrolyte?) stack comprising four cells, according to Science Direct

Jacinta: So continuing with Philip Russell’s simple video of a small hydrogen fuel cell (in the previous post), he explains that when the electrolysis process reverses itself, powering the fan, hydrogen is entering the cathode where it reacts with the palladium catalyst. The reaction with palladium is described as complex and weird, so he puts the matter off to a future video. In any case the hydrogen is split, producing electrons and hydrogen ions. Those electrons travel around the circuit which powers the fan, or a light bulb or some other electrical device, and the hydrogen ions travel through/across the PEM, where they react with the electrons in the circuit, and the oxygen, to produce water, which escapes from the anode side. 

Canto: So what they’re after in all this is the electrons, in sufficient abundance and in continuous supply to power whatever, without the use of carbon-based fuels. Frankly I’m not even sure how fossil fuels, hydrocarbons etc produce electricity, but hopefully I’ll learn something about this along the way.

Jacinta: You mean how does coal, oil or gas get transformed into high-energy electrons bumped along in a circuit? Yes, we have a lot to learn. 

Canto: And how do electrons in a wire make an air-conditioner work? But let’s stick with hydrogen for now. An older video, from 2012, from the excellent Fully Charged series, provides some other insights. I won’t go into too much detail with it, as the fuel cell described is very similar to Russell’s, but it does highlight some problems, at least from 2012. First, the interviewee, James Courtney from Birmingham University, uses the term proton-exchange membrane (PEM) rather than Russell’s PEM – a polymer exchange membrane. They mean the same thing, as the membrane is made of a polymer, and the key is that it’s an ‘electron insulator’, allowing protons to pass through. The polymer is usually nafion, a synthetic polymer created sixty years ago. It’s described as an ionomer for its ionic properties. But the most important thing I learned from Courtney is about the issue of platinum/palladium. It’s very very expensive, and its price is rising. Courtney – nine years ago – was experimenting with solid oxide electrolytes.

 Jacinta: From Wikipedia: 

solid oxide fuel cell (or SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte. Advantages of this class of fuel cells include high combined heat and power efficiency, long-term stability, fuel flexibility, low emissions, and relatively low cost. The largest disadvantage is the high operating temperature which results in longer start-up times and mechanical and chemical compatibility issues.

Canto: An organisation called Bloom Energy, self-described as ‘a leader in the SOFC industry’, has a bit to say about the technology. So, again we have the negative anode and the positive cathode, and the electrolyte in between which undergoes ‘an electrochemical reaction’…

Jacinta: That’s when the miracle occurs.

Canto: Yes, and this produces an electrical current. So here’s something to think about re electrolytes: 

The electrolyte is an ion conductor that moves ions either from the fuel to the air or the air to the fuel to create electron flow. Electrolytes vary among fuel cell types, and depending on the electrolyte deployed, the fuel cells undergo slightly different electrochemical reactions, use different catalysts, run on different fuels, and achieve varying efficiencies.

Does that help?

Jacinta: Yes, it helps to complicate matters. 

Canto: So the Bloom Energy website reckons that SOFCs have the best potential for fuel cell technology, and promises they’ll bear fruit in the next six years – instead of the usual five. Here’s their diagram of an SOFC.


Note that they’re using natural gas (methane) in a process called methane reformation, also mentioned by James Courtney. So, not exactly a clean technology, but also, as the illustration mentions, no precious metals, corrosive acids or molten materials. 

Jacinta: But apparently this isn’t a hydrogen fuel cell. Barely a mention of hydrogen. 

Canto: Yes, the illustration presents oxygen ions reacting with ‘fuel in the fuel cell’ to produce electricity. The cleanness comes from the fact that there’s no combustion, making it more sustainable and of course more green than combustion-based tech. Apart from a partial reduction in greenhouse gases, this tech does away with the emission of harmful sulphur dioxide and nitrogen oxide. And their ‘Bloom box’ fuel cell packs can run on hydrogen, with net zero carbon emissions. They see their technology being well suited to distributed networks and mini-grids, which may provide the power supplies of the future.

Jacinta: We shall see – if we live long enough. Meanwhile let’s look at another video, featuring Dr Stephen Carr, of the H2 Centre, University of South Wales, on how a hydrogen fuel cell works. Eventually it’ll all come together.

Canto: And then fall apart again. This video is more recent than the previous two, but I’m not sure that there have been any new developments in the interval. So Dr Carr presents ‘a demonstration kit of a renewable hydrogen energy storage system’, in which the hydrogen is produced by solar power…

Jacinta: Another magical moment?

Canto: Well, apparently. Anyway, he represents the sun with a lamp – so I suppose it’s a demonstration, not the real thing. The lamp shines on a PV (photovoltaic) panel which produces electricity.

Jacinta: Grrr, they never explain that bit.

Canto: How do you produce annoyance? Bet you can’t explain that either. Anyway, the electricity runs through an electrolyser, which splits water into oxygen and hydrogen, which is stored for times when we can’t directly produce power from the sun. At such times we can run the hydrogen and oxygen through a fuel cell (which seems to operate oppositely to an electrolyser) to produce electrical power. As he says (and this is new) the photons from the lamp (in lieu of the sun) are converted by the panel into electrical energy or power (but I think those are two distinct things). This is of course referring to how solar energy/power works, which is an entirely different thing. We’ll leave that aside for now, along with the big heap of other things.

Jacinta: Yes let’s just focus on what Dr Carr says. The electrical power powers an electrolyser. The electrons are used to drive an electrochemical process which splits water into hydrogen and oxygen. On one side of this electrolyser the water is ‘split into hydrogen’ and on the other side it produces oxygen (magic happens). Then the hydrogen and oxygen can be stored until required, when we can somehow convert these elements into electricity. We can observe, as in the Philip Russell video, bubbles of hydrogen and oxygen forming on either side of the electrolyser, and being collected and stored. 

Canto: So we’re again not going to discover the detailed physics/chemistry of all this, but apparently we now have stored power. And this gets run backwards through the fuel cell. In the fuel cell, the released oxygen and hydrogen, in a reverse process to electrolysis (I think), produces pure, apparently drinkable water, and electricity. So the two gases are released from the electrolyser into the fuel cell, oxygen at one electrode, hydrogen at the other, and they’re combined and subjected to electrochemical processes (more magic), producing water and electricity sufficient in this tiny demo model to power a fan or small light. So far, precisely as enlightening as the Philip Russell video.

Jacinta: So next we’re taken to a big electrolyser, something like the new one at Tonsley, South Australia. It uses a stack of some 80 fuel cells to produce stacks of hydrogen. The electrolyser takes in about 50kw of power and produces about 1 kilogram of hydrogen per hour – which means very little to me. 

Canto: It’s good that they know this I suppose. So they have an electrolysis stack, and they feed in ‘pure de-ionised water’ – I bet we could do a whole post on that – and apply DC electric power – another post’s worth – which splits the water into hydrogen and oxygen.

Jacinta: When I think of AC and DC I think of Tesla v Edison. History is so much easier than science. I think we need to do a basic course in electricity. But continuing with Dr Carr, for what it’s worth to us, he says that ‘everything else in this unit is gas clean-up’. The hydrogen is ‘de-watered’ to make sure it’s completely dry, and it’s also de-oxygenated, in other words thoroughly purified. Then, for storage, it’s compressed to 200 bar, meaning 200x atmospheric pressure.

Canto: The bar, presumably for barometric pressure, is commonly used in Europe but not accepted by the US, centre of arseholedom with regard to weights and measures. 

Jacinta: The trouble is that ‘atmosphere’ for measures of atmospheric pressure, is highly contestable. Anyway, we’ll finish this off next time, for now I’ll just say that Elon Musk is still not much impressed with hydrogen technology, saying that hydrolysis is way too energy-intensive-expensive, that methane or propane etc extraction defeats the purpose, that hydrogen is too light to store easily, that it’s very volatile etc, but maybe it could work for aircraft in the future… So why is so much money being expended on it, in so many countries? Why is it suddenly such a big deal? That’s a ‘mystery’ we’ll have to investigate… 


The Hydrogen fuel cell explained, clean energy, by Philip Russell, youtube video

Hydrogen Fuel Cells | Fully Charged, youtube video

How does a hydrogen fuel cell work, with Dr Stephen Car, video

Elon Musk about Hydrogen Cars, video

Written by stewart henderson

July 7, 2021 at 9:27 pm

a hydrogen energy industry in South Australia?

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an artist’s impression of SA’s hydrogen power project

I recently received in the mail a brochure outlining SA Labor’s hydrogen energy jobs plan, ahead of the state election in March 2022. The conservatives are currently in power here. The plan involves building ‘a 200MW hydrogen fuelled power station to provide firming capacity in the South Australian Electricity Market’.

So, what does a ‘hydrogen fuelled power station’ entail, what is ‘firming capacity’ and what does 200MW mean?

A presumably USA site called tells me this:

Hydrogen is a clean fuel that, when consumed in a fuel cell, produces only water. Hydrogen can be produced from a variety of domestic resources, such as natural gas, nuclear power, biomass, and renewable power like solar and wind. These qualities make it an attractive fuel option for transportation and electricity generation applications. It can be used in cars, in houses, for portable power, and in many more applications. Hydrogen is an energy carrier that can be used to store, move, and deliver energy produced from other sources.

This raises more questions than answers, for me. I can understand that hydrogen is a clean fuel – after all, it’s the major constituent, molecularly speaking, of water, which is pretty clean stuff. But what exactly is meant by ‘clean’ here? Do they mean ‘carbon neutral’, one of today’s buzz terms? Presumably so, and obviously hydrogen doesn’t contain carbon. Next question, what exactly is a fuel cell? Wikipedia explains:

A fuel cell is an electrochemical cell that converts the chemical energy of a fuel (often hydrogen) and an oxidizing agent (often oxygen) into electricity through a pair of redox reactions. Fuel cells are different from most batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy usually comes from metals and their ions or oxides that are commonly already present in the battery, except in flow batteries. Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied.

So the planned 200 megawatt power station will use the chemical energy of hydrogen, and oxygen as an oxidising agent, to produce electricity through a pair of redox reactions. Paraphrasing another website, the electricity is produced by combining hydrogen and oxygen atoms. This causes a reaction across an electrochemical cell, which produces water, electricity, and some heat. The same website tells me that, as of October 2020, there were 161 fuel cells operating in the US with, in total, 250 megawatts of capacity. The planned SA power station will have 200 megawatts, so does that make it a gigantic fuel cell, or a fuel cell collective? In any case, it sounds ambitious. The process of extracting the hydrogen is called electrolysis, and the devices used are called electrolysers, which will be powered by solar energy. Excess solar will no longer need to be switched off remotely during times of low demand.

There’s no doubt that the fortunes of hydrogen as a clean fuel are on the rise. It’s also being considered more and more as a storage system to provide firming capacity – to firm up supply that intermittent power sources – solar and wind – can’t always provide. The completed facility should be able to store 3600 tonnes of hydrogen, amounting to about two months of supply. There are export opportunities too, with all this excess supply. Japan and South Korea are two likely markets.

While it may seem like all this depends on Labor winning state government, the local libs are not entirely averse to the idea. It has already installed the nation’s largest hydrogen electrolyser (small, though, at 1.25 MW) at the Tonsley technology hub, and the SA Energy Minister has been talking up the idea of a hydrogen revolution. The $11.4 million electrolyser, a kind of proof of concept, extracts hydrogen gas from water at a rate of up to 480 kgs per day.

The difference between the libs and labor it seems is really about who pays for the infrastructure. Unsurprisingly, the libs are looking to the private sector, while Labor’s plans are for a government-owned facility, with the emphasis on jobs. Their brochure on the planned power station and ancillary developments is called the ‘hydrogen jobs plan’. According to SA’s Labor leader, Peter Malinauskas, up to 300 jobs will be created in constructing the hydrogen plant, at least 10,000 jobs will be ‘unlocked from the $20bn pipeline of renewable projects in South Australia’ (presumably not all hydrogen-related, but thrown in for good measure) and 900+ jobs will be created through development of a hydrogen export industry. He’s being a tad optimistic, needless to say.

But hydrogen really is in the air these days (well, sort of, in the form of water vapour). A recent New Scientist article, ‘The hydrogen games’, reports that Japan is hoping that its coming Olympic and Paralympic Games (which others are hoping will be cancelled) will be a showcase for its plan to become a ‘hydrogen society’ over the next few decades. And this plan is definitely good news for Australia.

Japan has pledged to achieve net-zero greenhouse gas emissions by 2050. However, this is likely impossible to achieve by solar or other established renewables. There just isn’t enough available areas for large scale solar or wind, in spite of floating solar plants on its lakes and offshore wind farms in planning. This is a problem for its hydrogen plans too, as it currently needs to produce the hydrogen from natural gas. It hopes that future technology will make green hydrogen from local renewables possible, but meanwhile it’s looking to overseas imports, notably from Australia, ‘which has ample sunshine, wind and empty space that make it perfect for producing this fuel’. Unfortunately we also have an ample supply of empty heads in our federal government, which might get in the way of this plan. And the Carbon Club, as exposed by Marian Wilkinson in her book of that name, continues to be as cashed-up and almost thuggishly influential as ever here. The success of the South Australian plan, Labor or Liberal, and the growing global interest in hydrogen as an energy source – France and Germany are also spending big on hydrogen – may be what will finally weaken the grip of the fossil fuel industry on a country seen by everyone else as potentially the best-placed to take financial advantage of the green resources economy.


Hydrogen Jobs Plan: powering new jobs & industry (South Australian Labor brochure)

‘The hydrogen games’, New Scientist No 3336 May 2021 pp18-19

Marian Wilkinson: The Carbon Club: How a network of influential climate sceptics, politicians and business leaders fought to control Australia’s climate policy, 2020

Written by stewart henderson

June 24, 2021 at 7:49 pm

notes on the electrification of air travel

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stolen from NASA – hope I didn’t let the batt out of the bag

Air travel has become noticeably more popular over the past few decades – due largely to affordability. Even I can afford to catch a plane occasionally these days. And yet …

I realised something was out of kilter when I discovered that, in Europe, you can fly relatively cheaply from one major city to another by plane, whereas travelling by train costs more (sometimes much more) while being more efficient in terms of carbon emissions. So why is that, and what can be done about it?

Planes are generally more costly to run and, especially, to maintain than trains, and labour costs, too, are higher. Yet some of the larger airline companies are prepared to lose money on high-demand short-haul flights to maintain their profile, knowing they can gain on international flights. They can also be (or are) more flexible with their pricing, as this article points out, so that they can get bums on seats at suddenly slashed rates, filling their aircraft for each flight, unlike trains, which have basically operated under the same half-arsed system for over a century.

So, with the steady increase in domestic and international flights, and the lack of government oversight – e.g. taxation – of international airlines that transcend political borders, the carbon footprint of air flight (if that makes sense) is growing. A 2018 report on CO2 emissions stated that ‘using aviation industry values’ there was a 32% increase in aviation emissions in the previous five years. Which of course raises the question – how do we solve the problem of over-use of costly, environmentally-unfriendly jet fuel? The answer, of course, is electric propulsion. No? An electric motor is far simpler and easier to maintain than a jet engine (a turboprop engine has between 7000 and 10,000 moving parts). Energy costs are also cheaper, once a few problems are worked out – ahem.

The biggest problem, of course, is the battery. I’ve heard that AA batteries mightn’t be enough. Nor are the current generation of lithium-ion batteries, though innovation and research in this area is being driven by electric cars hoho. Clearly electric aircraft have to start small and short-haul, and they’re already doing so. I’ve written about this before, but it’s time for an update. Some of the companies involved include Pipistrel, Harbour Air and Eviation, but this is still extremely small-scale stuff as everybody waits for the battery boffins to perform the next miracle. Meanwhile, as with the motor vehicle industry, hybrids have been developed as a kind of stop-gap for larger capacity flights. Another company, Ampaire, has developed small hybrid aircraft with which it hopes to start daily operations in Hawaii in the near future. It’s also working in Norway, where they’re hoping to have all flights of 90 minutes or less to be be either fully electric or hybrid by 2040. I’m glad to hear that my birth country, Scotland is also investing in electric and hybrid planes for similar purposes. If these planes could be shown to be economically viable, then larger aeroplane companies will surely invest in them, as they tend to lose money on regional routes (small turbine engines being very inefficient). This could be the real game-changer, providing reason to invest in battery and other technology for longer electric flight. Changes in technology, combining standard aircraft design with helicopter design, are likely to make air flight more personalised in future, with less need to depend on airports. Of course this will come with regulatory and other issues, but it all makes for a more interesting future in the sky….


Why don’t we have electric planes yet? CNBC video

Written by stewart henderson

December 29, 2019 at 4:14 pm

Electric aircraft? It’s happening, in a small way

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the Ampaire 337

I no longer write on my solutionsok blog, as it’s just easier for a lazy person like me to maintain the one site, but as a result I’ve not been writing so much about solutions per se, so I’ll try to a bit more of that. The always entertaining and informative Fully Charged show on YouTube provides plenty of material about new developments in renewable energy, especially re transport, and in a recent episode, host Robert Llewelyn had a bit to say about electric planes, which I’d like to follow up on.

Everyone knows that plane travel has been on the up and up haha for decades, and you may have heard that these planes use up a lot of fossil fuel and produce lots of nasty emissions. According to the Australian government’s Department of Infrastructure and Many Other Things (DIMOT – don’t look it up) Australia’a civil aviation sector contributed 22 million tonnes of CO2-equivalent emissions in 2016. That’s of course a meaningless number but safe to say it’s dwarfed by the emissions of the major aviation countries. I assume the term ‘C02-equivalent’ means other greenhouse gases converted into equivalent-impacting amounts of CO2. For aircraft this includes water vapour, hydrocarbons, carbon monoxide, nitrogen oxides, lead and other atmosphere-affecting nasties. More innovative and less polluting engine designs have failed to halt the steady rise of emissions due to increased air travel worldwide, and there’s no end in sight. It’s really the only emissions sector for which there is no obvious solution – unlike other sectors which are largely blocked by vested interests.

So, while few people at present see electric aircraft as the big fix, enterprising engineers are making steady improvements and trying for major breakthroughs with an eye to the hopefully not-too-distant future. Just a couple of days ago, as reported on the nicely-named Good News Network, the largest-ever hybrid-electric aircraft (it looks rather small), the Ampaire 337, took flight from Camarillo airport in California (of course). The normally twin-engine plane was retrofitted with an electric motor working in concert with the remaining fuel engine to create a ‘parallel hybrid’, which significantly reduces emissions. After this successful test run, there will be multiple weekly flights over the next few months, and then, if all goes well, commercial short-haul flights are planned for Hawaii.

Of course, here in Australia, where electric cars are seen by power-brokers as some kind of futuristic horror set to destroy our way of life, there’s no obvious appetite for even wierder flying things, but our time will come – or perhaps we should all give up and invade western Europe or California. Meanwhile, Fully Charged are saying ‘there’s no shortage of aircraft companies around the world [including Rolls Royce] developing electric aircraft’, as well as converting light aircraft to electric (the Ampaire 337 mentioned above is actually a converted Cessna 337). A Canadian airline, Harbour Air, is converting 3 dozen seaplanes to electric motors, with first passengers flights expected by late 2021. These will only be capable of short flights in the region of British Columbia – range, which is connected to battery weight, being perhaps the biggest problem for electric aircraft to overcome. Again according to Fully Charged, there are over 100 electric aircraft development programs going on worldwide at present, and we should see some results in terms of short-haul flights in five years. Perfect for Europe, but also not out of the question for Adelaide to Melbourne or Port Lincoln, Canberra to Sydney and so on. Norway has a plan to use electric aircraft for all its domestic passenger flights in the not-too-distant future.

A name dropped on Fully Charged, Roei Ganzarski, seems worth following up. He says ‘By 2025, 1000 miles in an electric plane is going to be easily done. I’m not saying 5000 miles, but 1000 miles, easily.’ Ganzarski is currently the CEO of magniX, an ‘electric propulsion technology company’, based in Seattle. His company made the motors for the Ampaire 337, I think.

It should be pointed out that UAVs (unmanned – or unpersonned? – aerial vehicles), aka drones, are small electric aircraft, so the principle of electric flight is well established. It’s also worth noting that electricity doesn’t have to come from batteries, though they’re the most likely way forward. Solar cells, for example, can directly convert sunlight into electricity, and in 2015/16, using two alternating pilots, Solar Impulse 2 became the first fixed-wing, piloted, solar-powered aircraft to circumnavigate the globe. Fuel cells, particularly using hydrogen, are another option.

At the moment, though, hybrid power is all the go, and the focus is on light aircraft and short-haul flight. General aviation is still a long way off because, according to this Wikipedia article, ‘the specific energy of electricity storage is still 2% of aviation fuel’. As to what that means, I have very little idea, but this steal from a Vox piece on the topic helps to clarify:

The key limitation for aircraft is the energy density of its fuel: When space and weight are at a premium, you want to cram as much energy into as small a space as possible. Right now, some of the best lithium-ion batteries have a specific energy of 250 watt-hours per kilogram, which has already proved viable in cars. But to compete on air routes up to 600 nautical miles in a Boeing 737- or Airbus A320-size airliner, Schäfer estimated that a battery would need to have a specific energy of 800 watt-hours per kilogram. Jet fuel, by comparison, has a specific energy of 11,890 watt-hours per kilogram.

So, specific energy is essentially related to energy density, and I know that getting batteries to be as energy-dense as possible is the holy grail of researchers. So, until that ten-fold or 100-fold improvement in energy density is achieved by the battery of batteriologists beavering away at the big plane problem, we should at least push for light aircraft and short-haul flights to go completely electric asap. Ausgov, do us proud.

Written by stewart henderson

June 12, 2019 at 9:47 am

towards James Clerk Maxwell 3 – Benjamin Franklin and Coulomb’s Law

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Coulomb’s law – attraction and repulsion

Canto: So we’ve been looking at electricity and magnetism historically, as researchers, scientists, thinkers, experimenters and so on have managed to piece these processes together and combine them into the one thing, electromagnetism, culminating in J C Maxwell’s equations…

Jacinta: Or going beyond those equations into the implications. But of course we’re novices regarding the science and maths of it all, so we should recommend that real students of this stuff should go to the Khan academy lectures, or Matt Anderson’s lectures for the real expert low-down. As will we. But we need to point out, if only to ourselves, that what we’re trying to get our heads around is really fundamental stuff about existence. Light, which is obviously fundamental to our existence, is an electromagnetic wave. So, think magnetism, think electricity, and think light.

Canto: Right, so we’re going back to the eighteenth century, and whatever happens after Hauksbee and Polinière.

Jacinta: Well, scientists – or shall we say physical scientists, the predecessors of modern physicists – were much influenced throughout the eighteenth century by Newton, in particular his inverse square law of gravity:

F=G{\frac {m_{1}m_{2}}{r^{2}}}\

Newton saw gravity as a force (F), and formulated the theory that this force acted between any two objects (m1 and m2 – indicating their masses) in a direct line between their respective centres of mass (r being the length of that line, or the distance between those centres of mass). This force is directly proportional to the product of the two masses and inversely proportional to the distance. As to G, the gravitational constant, that’s something I don’t get, as yet. Anyway, the success of Newton’s theory, especially the central insight that a force diminishes, in a precise way, with distance, affected the thinking of a number of early physical scientists. Could a similar theory, or law (they didn’t think in terms of theory then) apply to electrical forces? Among those who suspected as much were the mathematician Daniel Bernoulli, who made major contributions to fluid dynamics and probability, and Alessandro Volta, who worked on electrical capacitance and storage, the earliest batteries.

Canto: And Joseph Priestley actually proposed an inverse square law for electricity, but didn’t work out the details. Franz Aepinus and Benjamin Franklin were also important 18th century figures in trying to nut out how this force worked. All of this post-Newtonian activity was putting physical science on a more rigorous and mathematical footing. But before we get to Coulomb and his law, what was a Leyden Jar?

Jacinta: Leyden jars were the first capacitors. They were made of glass. This takes us back to the days of Matthias Bose earlier in the 18th century, and even back to Hauksbee. Bose, a professor of natural philosophy at the University of Wittenberg, worked with and improved Hauksbee’s revolving glass-globe machine to experiment with static electricity. He added a metal ‘prime conductor’ which accumulated a higher level of static charge, and gave spectacular public demonstrations of the sparks he created, using them to set alcohol alight and to create ‘beatification’ effects on a woman wearing a metal helmet. All great japes, but it promoted interest in electricity on the continent. The trick with alcohol inspired another experimenter, Jurgen von Kleist, to invent his Leyden jar, named for Kleist’s university. It was a glass container filled with alcohol (or water) into which was suspended a metal rod or wire, connected to a prime conductor. The fluid collected a great deal of electric charge, which turned out to be very shocking to anyone who touched the metal rod. Later Leyden jars used metal foil instead of liquid. These early capacitors could store many thousands of volts of electricity.

Canto: At this time, in the mid-eighteenth century, nobody was thinking much about a use for electricity, though I suppose the powerful shocks experienced by the tinkerers with Leyden jars might’ve been light-bulb moments, so to speak.

Jacinta: Well, take Ben Franklin. He wasn’t of course the first to notice that electrostatic sparks were like lightning, but he was possibly the first to conduct experiments to prove the connection. And of course he knew the power of lightning, how it could burn down houses. Franklin invented the lightning rod – his proudest invention – to minimise this damage.

Canto: They’re made of metal aren’t they? How do they work? How did Franklin know they would work?

Jacinta: Although the details weren’t well understood, it was known in Franklin’s time that some materials, particularly metals (copper and aluminium are among the best), were conductors of electricity, while others, such as glass, were insulators. He speculated that a pointed metal rod, fixed on top of buildings, would provide a focal point for the electrical charge in the clouds. As he wrote: “The electrical fire would, I think, be drawn out of a cloud silently, before it could come near enough to strike….” He also had at least an inkling of what we now call ‘grounding’, as per this quote about the design, which should use “upright Rods of Iron, made sharp as a Needle and gilt to prevent Rusting, and from the Foot of those Rods a Wire down the outside of the Building into the Ground”. He was also, apparently the inventor of the terms negative and positive for different kinds of charge.

Canto: There are different kinds of charge? I didn’t know that.

Jacinta: Well you know of course that a molecule is positively charged if it has more protons than electrons, and vice versa for negative charge, but this molecular understanding came much later. In the eighteenth century electricity was generally considered in terms of the flow of a fluid. Franklin posited that objects with an excess of fluid (though he called it ‘electrical fire’) were positively charged, and those with a deficit were negatively charged. And those terms have stuck.

Canto: As have other other electrical terms first used by Franklin, such as battery, conductor, charge and discharge.

Jacinta: So let’s move on to Charles-Augustin De Coulomb (1736-1806), who was of course one of many scientists and engineers of the late eighteenth century who were progressing our understanding and application of electricity, but the most important one in leading to the theories of Maxwell. Coulomb was both brilliant and rich, at least initially, so that he was afforded the best education available, particularly in mathematics…

Canto: Let me write down Coulomb’s Law before you go on, because of its interesting similarity to Newton’s inverse-square gravity law. It even has one of those mysterious ‘constants’:

{\displaystyle F=k_{e}{\frac {q_{1}q_{2}}{r^{2}}},}

where F is the electrostatic force, the qs are particular magnitudes of charges, and r is the distance between those charges.

Jacinta: Yes, the Coulomb constant, ke, or k, is a constant of proportionality, as is the gravitational constant. Hopefully we’ll get to that. Coulomb had a varied, peripatetic existence, including a period of wise retirement to his country estate during the French revolution. Much of his work involved applied engineering and mechanics, but in the 1780s he wrote a number of breakthrough papers, including three ‘reports on electricity and magnetism’. He was interested in the effect that distance might have on electrostatic force or charge, but it’s interesting that these papers placed electricity and magnetism together. His experiments led him to conclude that an inverse square law applied to both.

Canto: I imagine that these constants required a lot of experimentation and calculation to work out?

Jacinta: This is where I really get lost, but I don’t think Coulomb worked out the constant of proportionality, he simply found by experimentation that there was a general law, which he more or less stated as follows:

The magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.
The force is along the straight line joining them. If the two charges have the same sign, the electrostatic force between them is repulsive; if they have different signs, the force between them is attractive.

It seems the constants of proportionality are just about units of measurement, which of course were different in the days of Coulomb and Newton. So it’s just about measuring stuff in modern SI units using these laws. It’s about conventions used in everyday engineering, basically. I think.

Canto: Equations like these have scalar and vector forms. What does that mean?

Jacinta: Basically, vector quantities have both magnitude and direction, while scalar quantities have magnitude only. The usual example is speed v velocity. Velocity has magnitude and direction, speed only has magnitude. Or more generally, a scalar quantity has only one ‘dimension’ or feature to it in an equation – say, mass, or temperature. A vector quantity has more than one.

Canto: So are we ready to tackle Maxwell now?

Jacinta: Hell, no. We have a long way to go, with names like Gauss, Cavendish and Faraday to hopefully help us along the path to semi-enlightenment. And I think we need to pursue a few of these excellent online courses before we go much further.


Khan academy physics (160 lectures)

Matt Anderson physics (191 lectures)

Written by stewart henderson

May 18, 2019 at 6:04 pm

Towards James Clerk Maxwell 2 – Francis Hauksbee’s experiments

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an electrostatic generator – one of Hauksbee’s many ingenious experimental devices

Canto: So we’ve witnessed electricity since we’ve had the wit to witness, in lightning. And through our attempts to understand and harness those scary bursts of energy we’ve transformed our world.

Jacinta: We’ve written about lightning before, but the info we presented there was accumulated over centuries. Now we’re going to travel back to the early years of the Royal Society in England, the early 1700s, a mere 300 years ago, to reflect on the first experiments with electricity – remembering that there was no electric power and light in those days, that gods were in the air and much was mysterious.

Canto: Electricity from the start was much sexier, and scarier, than magnetism – lightning very very frightning was the most obvious physical manifestation, and its power was easily recognised. It could kill at a stroke, while magnetism seemed all about metals getting stuck together, and needles pointing north. Interesting, but hardly earth-shattering.

Jacinta: Lightning was all about gigantic sparks shattering the sky, and the ancients, who spent so much of their time in darkness, must have seen other, less impressive and dangerous sparks, the sparks of static electricity, and wondered.

Canto: In the recent BBC documentary The story of electricity, narrator Jim Al-Khalili begins by describing Francis Hauksbee‘s experiments with static electricity and electroluminescence in the early 1700s, which dazzled visitors to the Royal Society. These were the first properly documented experiments with the mysterious force, and a collection of his papers describing these experiments was widely read by the 18th century cognoscenti – including Joe Priestley and Ben Franklin. He employed the newly-invented air pump (simply a pump for pushing out air, as in a common bike pump), popularised in England by Robert Hooke some decades before. Hauksbee made his own improvements, enabling the pump to create a vacuum.

Jacinta: Yes Hauksbee was a more interesting figure than The story of electricity presents. He didn’t ‘lose interest’ but worked on his experiments and reflected on them until his final illness in 1713 – and I’m thinking that illness, since he was only in his late forties – may have been due to mercury poisoning. Hauksbee was ‘lower class’ so few details of his life are documented. However, in these experiments he wasn’t thinking so much of electricity as of ‘attractive forces’. Also as an experimenter who must always have seen himself as an underling (in his book he mentions his ‘want of a learned education’), he doubtless felt obliged to follow the guidance of his Royal Society ‘master’, Newton, which took him into different fields of research….

Canto: The term ‘electricity’ was possibly not in common use then? You’re right, though, about Hauksbee, who rose from obscurity to become a member of the Royal Society, probably under the auspices of Newton. In late 1705, as a result of some spectacular effects displayed to the Society he became intrigued by ‘mercurial phosphorus’. The fact that mercury, in a vacuum, glowed when shaken, had already been noted by Jean Picard, a 17th century French astronomer, and the Swiss mathematician Johann Bernoulli.

Jacinta: And this has to do with electricity?

Canto: We shall see. Hauksbee wanted to work out the conditions under which this mercurial light was produced. He found that the more air in the container, the weaker the light. Also the light’s intensity depended on the movement of the mercury. He concluded that the friction of the mercury against the glass was the major cause. But was it only mercury that had this property, and was it only glass that brought it out? He experimented with other materials, finding a means of rubbing them together in a section of his air pump, Amber rubbed with wool produced a light, brightened in the absence of air. By contrast metal on flint only produced sparks when air was present. Remember, oxygen wasn’t known about at the time. In late 1705 Hauksbee presented one of his most spectacular experiments for the Society. Ingenious instrument-maker that he was, he created a glass globe, from which air could be pumped in and out, on a rotating spindle. The spinning globe came into contact with woollen cloth, and the contact created a weird purple light inside the evacuated globe, which reduced as air was let in. It was a fantastic mystery.

Jacinta: I’m hoping you can solve it.

Canto: Great expectations indeed. He experimented further, and found that when he pressed his own hands against a spinning evacuated globe, the same bright purple glow was produced, which again faded when air was let in to the globe.

Jacinta: Okay, what Hauksbee was exploring in these experiments are what we now call triboelectric effects. I remember playing around with this in schooldays by rubbing a plastic pen along the sleeve of my jersey and watching the fibres stand on end as the pen passed, and hearing the prickling sound of static electricity. The pen was then capable of lifting scraps of paper from the desk, for a time. But I didn’t see any purple lights and I’m not sure how the presence or absence of air relates to it all.

Canto: Yes, triboelectricity is about the exchange of electric charge between different materials – the build-up and discharge of electrical energy. It seems that some materials have a more or less positive charge and some have a more or less negative or opposite charge (because positive and negative are really arbitrary terms, the key point is their relation to each other), and we know that like charges repel and opposite charges attract.

Jacinta: You’ve brought up the word ‘charge’ here, and I’m wondering if that’s just an arbitrary word too – like degree of positive charge just means degree of being repulsed by its opposite, negative charge. In other words, different materials are attracted to or repulsed by each other to varying degrees under various conditions, and that degree or ‘amount’ of attraction or repulsion is referred to as ‘charge’. So ‘charge’ is a relational term…

Canto: Ummm. Maybe. In any case, if you take these different materials down to the atomic level, and I’m not sure how you take plastic and wool down to that level – I mean I know plastic is a petrochemical product, but wool, which I’ve just looked up, has a very complex chemistry – but the fact that the plastic pen, after some rubbing, pulls the fibres of your woollen sleeve towards it is because there’s an attractive force operating between opposite charges. In fact there’s a movement of electrons between the materials, from the wool to the plastic. This electron transfer leaves those woollen fibres with a net positive charge, which is attracted to the now negatively charged plastic due to the electron flow. I think.

Jacinta: Mmm. None of this was understood in the early eighteenth century, obviously. But before we go back there, we’ll stay with this concept of charge, which is nowadays calculated as a fundamental or base unit, based on the electron or its opposite, charge-wise, the proton. These elementary particles have the same but opposite charge, though they’re very different in mass (something which seems suspect to me). Anyway, taking things on trust, a unit of charge is ‘defined’ in standard macro terms as a coulomb, named for the 18th century French physicist Charles-Augustin de Coulomb. One coulomb equals approximately 6.24 x 1018 protons (or electrons). We’ll come back to this later, no doubt. Returning to Hauksbee’s experiments, he soon realised that it was the glass, not the mercury inside it, that was the agent of electrical effects. His experiments with glass globes were written down in great detail, a boon to later researchers.

Canto: Interestingly, I’ve discovered that, more or less exactly at the same time, one Pierre Polinière was conducting and presenting experiments on electroluminescence in Paris:

A closer examination of these experiments reveals not only that Polinière had personally presented them before the French Academy of Sciences, but that Polinière and Hauksbee, starting from a common interest in the ‘mercurial phosphor’, had conducted similar investigations and had in fact simultaneously announced their independent discoveries of the luminescence of evacuated glass containers.

Pierre Polinière, Francis Hauksbee and electroluminescence: a case of simultaneous discovery.
David Corson, 1968.

Jacinta: So we might finish by trying to explain our current understanding of electroluminescence (EL) and its applications. It’s a sort of combo of electricity and light, as you can imagine, or electrons and photons on the level of particles. For example, semiconductors emit light when subjected to a strong electric field or current….

Canto: Is that the basis of LED lighting?

Jacinta: Absolutely. Electrons in the semiconductor material recombine with electron holes, emitting energy in the form of photons. So it has taken us three centuries to really effectively harness the electroluminescent effects demonstrated by Hauksbee in the early days of the Royal Society.

Canto: What are electron holes? I’m thinking not ‘holes in electrons’ but holes left by electrons as they’re displaced in an electric current?

Jacinta: Yes, or almost. It’s like the lack of an electron where you might expect an electron to be. These holes where you might expect an electrically charged particle (an electron) to be, act like positively charged particles – a positron, say – and move through a lattice like an electron does. We could get into very complicated electronics here, if we had the wherewithal, but these holes are examples of quasiparticles, which mostly exist within solids. Fluid movement within solids (not apparently a contradiction in terms) is extremely complicated. Who would’ve thunk it? This movement of electrons and protons within solids is ‘regulated’ by Coulomb’s Law. Remember him? We’ll be getting to that law very soon, as it’s essential to the field of electromagnetism. And that’s our topic don’t forget.

towards James Clerk Maxwell: 1 – a bit about magnetism

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the terrell, or model globe, with which Gilbert conducted experiments

Canto: So what do you know about magnetism?

Jacinta: Well not a lot but I’m hoping to learn a lot. Some metals – but perhaps it’s only iron – appear to be attracted by other metals – or other bits of iron – so that they’re pulled together and are hard to pull apart, depending on the strength of the magnetism, which is apparently some kind of force. And I believe it’s related to electricity.

Canto: We shall learn more together. All this enquiry stems from a perhaps vague interest in James Clerk Maxwell, who famously connected electricity and magnetism in an equation, or a series of equations, or laws, with a great deal of mathematical sophistication, which I don’t have. Maxwell is hardly a household name in the way that Newton and Einstein are, but he’s undoubtedly revered among mathematical physicists. My own interest is twofold – I’d like to understand more about physics and maths in general, and – I’m Scottish, sort of. That is, I was born there and grew up among Scottish customs, though I’ve lived in Australia since I was five, and I always like to say that I haven’t a nationalist cell in my body. I’ve never waved a flag or sung any of those naff national anthems, and I have dual British/Australian citizenship only as a matter of convenience – and I suppose the more nations I could become a citizen of, the more convenient it would be. And yet. I’ve always felt ‘something extra’ in noting the Scottish contribution to the sciences and the life of the mind. James Hutton, Charles Lyell, James Watt, Adam Ferguson, David Hume and Adam Smith are names I’ve learned with a glimmer of unwonted or irrational pride over the years, though my knowledge of their achievements is in some cases very limited. And that limitation is perhaps most extreme in the case of Maxwell.

Jacinta: So we’ll get back to him later. There are good, easily available videos on all matters scientific these days, so I’ve looked at a few on magnetism, and have learned a few things. Magnetism apparently occurs when the atoms in a block of material are all aligned in the same direction, because atoms themselves are like tiny magnets, they’re polarised with a north and south pole, which I think has something to do with ionisation, maybe. Most materials have their atoms aligned in an infinity of orientations, with a net effect of no magnetism. Don’t quote me on that. The Earth itself is a gigantic magnet with a north and south pole. If it wasn’t, then the solar wind, which is a plasma of charged particles, would strip away the ozone that protects us from UV radiation. Because that field is sucked in at the poles, we see that plasma in the northern and southern latitudes, e.g. the northern lights. We now know that magnetism is essential to our existence – light itself is just a form of electromagnetic radiation (I think). But what we first learned about this stuff was pretty meagre. There were these rocks called lodestones, actually iron ore (magnetite), which attracted iron objects – swords and other tools of the iron age. What was this invisible force? It was named magnetism, after the region of Magnesia in what’s now modern Greece, where presumably lots of these lodestones were to be found. Early discoveries about magnetism showed that it could be useful in navigation…

Canto: But that wasn’t too early – there’s something of a gap between the discussions in Aristotle and Hippocrates and the 12th century realisation that a magnetic needle could be used for navigation. At least in Europe. The Chinese were well ahead in that regard. But I should stop here and say that if we’re going to arrive at Maxwell, it’s going to be a long, though undoubtedly fascinating road, with a few detours, and sometimes we might move ahead and turn back, and we’ll meet many brilliant characters along the way. And, who knows, we may never even arrive at Maxwell, and of course we shouldn’t assume that Maxwell is at the summit of all this.

Jacinta: So the first extant treatise on magnets was the Epistola de Magnete, by Petrus Peregrinus, aka Pete the Pilgrim, in 1269. It was described as a letter but it contained 13 chapters of weighty reading. The first 10 chapters apparently describe the laws of magnetism, a clear indication that such laws were already known. He describes magnetic induction, how magnetism can be induced in a piece of iron, such as a needle, by a lodestone. He writes about polarity, being the first to use the term ‘pole’ in this way – in writing at least. He noted that like poles repel and unlike poles attract, and he wrote of a south pole and a north pole. That’s to say, one end of a needle points north when given its head – for example when suspended in water. He also describes the ‘dry’ pivoted compass, which was clearly well in use by that time.

Canto: What he didn’t know was why a needle points north – actually magnetic north, which isn’t the same as the north pole – but close enough for most navigational purposes. He didn’t know that the Earth was a magnet.

Jacinta: On compass needles, there’s a neat essay online on how compasses are made. I’m not sure about how GPS is making compasses obsolete these days, but it’s a bit of a shame if it’s true…

Canto: So the next name, apart from the others, to associate with work on magnets was William Gilbert, who published De Magnete in 1600. This gathered together previous knowledge on the subject along with his own experimental work. One of the important things he noted, taken from the 1581 work The Newe Attractive, by Robert Norman, was magnetic inclination or dip, probably first noted by the Bavarian engineer and mathematician Georg Hartmann in the mid sixteenth century. This dip from the horizontal, either upward (steepest at the south pole) or downward (north pole) is a result of the Earth’s magnetic field, which doesn’t run parallel to the surface. Inspired by Norman’s work, Gilbert conducted experiments with a model Earth he made, concluding that the Earth was a magnet, and that its core, or centre, was made of iron…

Jacinta: Just how did he he work that out? Did he think that a bar magnet passed through the centre of the Earth from north to south pole?

Canto: I don’t think so, it’s probably more like he thought of Earth as a gigantic spherical lodestone with iron at its centre. It’s understandable that he would infer iron to be inside the Earth to make it magnetic, but he was the first to give a geocentric cause for the behaviour of compass needles – others had thought the attractive force was celestial. Interestingly, Gilbert was also a Copernican, in that he thought it absurd that the stars, which he believed to be vastly distant, revolved around the Earth. So he argued that the Earth turned, a view that got Galileo into so much trouble a few decades later.

Jacinta: Useful to be a Protestant in those times. Thank Dog for Henry VIII.

Canto: He also took an interest in what was later called electricity, though he didn’t consider it connected to magnetism. He built a versorium, the first electroscope, used to detect static electric charge. It was simply a metallic needle pivoted on a pedestal, like a compass needle but not magnetised. The needle would move towards a statically charged object, such as rubbed amber. In fact, Gilbert’s experiments strove to prove that static electricity was distinct from magnetism, which was an important development in early modern science.

Jacinta: I suppose we’re going to learn exactly what ‘static’ electricity is and how it fits in the over-all picture?

Canto: We shall try, though I shudder to think about what we’re embarking on here.

Jacinta: And I shudder to think about what cannot possibly be avoided – mathematics.

Canto: Well, yes, as we enter the 17th century, we’ll be encountering some great mathematical developments – with figures like Descartes, Pascal, Fermat, Liebniz and Newton all adding their weighty contributions to Galileo’s claim that nature is a book written in the language of mathematics.

Jacinta: Shit, I’m having a hard enough time trying to understand this stuff in English.

Canto: Hopefully it’ll be a great and rewarding adventure, and on the way we’ll learn about Coulomb’s inverse-square law, which is central to electrostatics. Meanwhile, it seems not much was added to our understanding of magnetism for a couple of hundred years, until Hans Ørsted’s more or less accidental discovery in 1819 that an electric current could create a magnetic field, by noting that a compass needle moved when placed near an electrified wire. Alessandro Volta had invented the voltaic pile, or battery, twenty years earlier, leading to a pile of electrical experiments in subsequent years.

Jacinta: But we’ll have to go back to the eighteenth century or beyond to trace developments in electricity before Ørsted’s finding brought the two fields together. And maybe we’ll look at the mathematics of
Charles-Augustin de Coulomb and others in the process. Let’s face it, we can’t progress towards Maxwell without doing so.

Canto: Tragic but true.

Written by stewart henderson

March 31, 2019 at 1:37 pm

technomagic – the tellingbone

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weirdly wired – the first telephone

The telephone remains the acme of electrical marvels. No other thing does so much with so little energy. No other thing is more enswathed in the unknown.

Herbert Casson ‘The history of the telephone”, 1910. Quoted in “The Information”, J Gleick

I recently had a conversation with someone of my generation about the technology of our childhoods, and how magical they seemed to us. So let me start with the motor car, or auto-mobile. Our first family car was a Hillman Minx, which was bought in maybe 1964 or so, not too long after we arrived in Australia. The model probably dated from the early or mid-fifties – we certainly weren’t wealthy enough to buy a brand new car. But that didn’t make it any less magical. How was it that you could turn a key and bring an engine to life, and with a bit of footwork and handiwork get the beast to move backward and forward and get its engine to putter or roar? I hadn’t the foggiest.

Next in the mid-sixties came the television box, fired by electrickery. Somehow, due to wires and signals, we could see a more or less fuzzy image of grey figures from faraway, giving us news of Britain and the World Cup, and shows from the USA like Hopalong Cassidy and the Cisco Kid, all made from faraway – even one day from the moon – for our entertainment and enlightenment. Wires and signals, I mean, WTF?

Next we became the first people in the street to have our own tellingbone (or that’s what we proudly told ourselves, actually we had no idea). So people would ring us from the other side of town and then talk to us as if they were standing right next to us!! It was crazy-making, yet people seemed generally to remain as sane as they had been. I would lie in bed trying to work it out. So someone would dial a number, and more or less instantaneously a ringing sound would come out of the phone miles and miles away, and a person there would pick up this bone-shaped piece of plastic with holes in it, and they would talk into one end and listen through the other end, and they could hear this person on the ‘end of the line’ miles away far better than they could hear someone else talking in the next room, all thanks, we were informed, to those wires and signals again.

So, forward to adulthood. One of the most informative books I’ve read in recent years is titled, appropriately enough, The Information, by James Gleick. It’s a history of information processing and communication from tribal drumming to the latest algorithms, and inter alia it tells the story of how the telephone became one of the most rapidly universalised forms of information transfer in human history in the period 1870-1900, approximately. And of course it didn’t come into existence out of nowhere. It replaced the telegraph, the first electrical telecommunications system, itself only a few decades old. Previous to this there were many experiments and developments in the field by the likes of Alessandro Volta, Johann Schweigger and Pavel Schilling. Studying electricity and its potential was the hottest of scientific activities throughout the 19th century, especially the first half.

The telegraph, though, was a transmission-reception system run by experts, making it very unlike the telephone. Gleick puts it thus:

The telegraph demanded literacy; the telephone embraced orality. A message sent by telegraph had first to be written, encoded and tapped out by a trained intermediary. To employ the telephone, one just talked. A child could use it.

Nevertheless the system of poles and wires, the harnessing of electricity, and the concepts of signal and noise (both abstract and exasperatingly practical) had all been dealt with to varying degrees of success well before the telephone came along.

So now let’s get into the basic mechanics. When we talk into a phone we produce patterned sound waves, a form of mechanical energy. Behind the phone’s mouthpiece is a diaphragm of thin metal. It vibrates at various speeds according to the patterned waves striking it. The diaphragm is attached to a microphone, which in the early phones consisted simply of carbon grains in a container attached to an electric current, which were compressed to varying degrees in response to the waves vibrating the diaphragm, modulating the current. That current flows through copper wires to a box outside your home which connects with other wires and cables in a huge telecommunications system.

Of course the miracle to us, or to me, is how a sound wave signal, moving presumably more or less at the speed of sound, and distinctive for every human (not to mention dogs, birds etc), can be converted to an electrical signal, moving presumably at some substantial fraction of the speed of light, then at the end of its journey be converted back to a mechanical signal with such perfect fidelity that you can hear the unmistakeable tones of your grandmother at the other end of the line in real time. The use of terms such as analogue and digitising don’t quite work for me, especially when combined with the word ‘simply’, which is often used. In any case, the process is commonplace enough, and has been used in radio, in recorded music and so forth.

It all bears some relation to the work of the greatest physical theorist of the 19th century, James Clerk Maxwell, who recognised and provided precise relationships between electrical impulses, magnetism and light, bringing the new and future technologies together, to be amplitude-modified by engineers who needed to understand the technicalities of input, output, feedback, multiplexing, and signal preservation. But as the possibilities of the new technology expanded, so did technological expertise, and switchboards and networks became increasingly complex. They eventually required a numbering system to keep track of users and connections, and telephone directories were born, only to grow in size and number, costing acres of forestry, until in the 21st century they didn’t. I won’t go into the development of mobile and smartphones here, those little black boxes of mystery which I might one day try to peer inside, but I think I’ve had enough armchair demystifying of the technomagical for one day.

Yet something I didn’t think of as a child was that the telephone was no more technomagical than just speaking and listening to the person beside you. To speak, to make words and sentences out of sounds, first requires a sound-maker (a voice-box, to employ a criminally simplistic term), then a complex set of sound-shapers (the tongue, the soft and hard palates, the teeth and lips) into those words and sentences. Once they leave the speaker’s lips they make waves in the air – complex and variable waves which carry to the hearer’s tympanum, stimulating nerves to send electrical impulses to the auditory cortex. This thinking to speaking to listening to comprehending process is so mundane to us as to breed indifference, but no AI process comes close to matching it.


The information, James Gleick, 2011

Written by stewart henderson

March 1, 2019 at 4:31 pm