Storm in a Teacup: The Physics of Everyday Life(76)

As the electrons shuffle through the metal of the heating element, they’re being pushed by the electric field. That makes them speed up slightly, but the conductor is made up of lots of atoms, and so these sped-up electrons inevitably bump into things. When they bump, they lose energy, heating up whatever they bumped into. And so forcing lots of charge to move means that there’s lots of bumping and lots of heating. That’s all the kettle is doing—speeding up electrons so that they bump into things and pass on their energy as heat. The electrons themselves don’t travel very far at all—they might drift at about 0.04 inch per second. But it’s enough.

Boiling water has loads of extra energy, and it’s amazing that it gets there just from minuscule electrons shuffling about and bumping into things. Amazing, yet undeniable; my tea is ready, heated by electric fields pushing on electrons in a conductor. This is the simplest possible use for electrical energy: converting it directly into heat. But once people had worked out how to build circuits and power supplies and batteries, things got much more sophisticated very quickly.

There is a fundamental difference between the electron dance generated by batteries (any batteries) and what happens when you plug a device into the wall outlet. In any device powered by a battery, the electrons are always flowing in one direction only. This is called direct current, or DC. A standard AA battery will supply about 1.5 volts DC. But the wall current is different—it’s alternating current, or AC. That means it switches direction about a hundred times a second.** It turns out to be more efficient if you run your electricity supply like this.

You can switch between DC and AC, but it’s a bit of a nuisance. Anyone who carries around a laptop power cable will be familiar with this kind of nuisance—it’s the small heavy block that sits in the middle of the cable. It’s called an AC/DC adapter, and its job is to convert the AC current from the outlet into the kind of DC current that your laptop wants (which is what the laptop battery provides directly). To do that, it needs coils of wire and a bit of circuitry, and it’s still tricky to make all the necessary bits any smaller.?? So for the time being, we’re stuck with carrying around the adapters.

We take electronics for granted today. But in its early days, it was a capricious and uncertain beast. My own grandfather was getting involved in that world just as all its new sophistication was making its way into our homes.

My grandfather, Jack, was one of the first television engineers. Back in his day, electronics could be loud and hot and were certainly capable of generating quite a pong—as my grandmother readily recalls. Her description of the sort of problem that he used to have to fix reminded me of that physicality about early electronics that’s easy to forget in these days of smartphones and Wi-Fi on tap – and also surprised me with her familiarity with all the components and processes. I’d never really heard her talk about anything technical in my life, and yet when it came to these old TVs, she was comfortable with specialized electrical terms I’d never come across. “Well,” she told me one day, “one important component was a line-output transformer, and when that went on the TV, it sometimes went with a bit of a bang but it also produced a burning sensation and a smell.” Her northern accent reminds me that this is almost certainly flat-capped understatement. Electrons have always been invisible, but from the 1940s to the 1970s you could definitely tell they were up to something. There was always the risk of a bang or a pop or a hiss, the sudden appearance of a sooty burnt patch or a flash of light that told you lots of energy had just been shunted somewhere it shouldn’t have gone. Jack found himself in at the beginning of the new world of television, part of the only generation that had a real feel for the electrical world. By the end of his career, transistors and computer chips had hidden it all away. The tiny exterior of these components conceals a vast and sophisticated interior, incomprehensible from the outside. But before they came along, there were a few decades when you could almost see the magic at work.

In 1935, at the age of sixteen, Jack had started a trade apprenticeship with Metropolitan Vickers, locally known as MetroVick. This giant of the heavy electronics engineering world was based in Trafford Park near Manchester, turning out world-class generators, steam turbines, and other large-scale electronics. When he finished his apprenticeship in electrical engineering at the age of twenty-one, he was classed as having a reserved occupation, deemed too useful to go to war, so he spent five years testing airplane gun electronics at MetroVick. The first test of these systems was called “flashing.” You put 2,000 volts across it and if it didn’t go bang, it passed. This was the raw end of the taming of the electron, the early stages of wrangling it into submission.

After the war, EMI was looking for people with electronics experience, because early televisions were skittish, complex beasts, needing an expert to set them up and frequent adjustment throughout their lifetimes. So EMI sent Jack to London to train as a television engineer. The tools of this trade were valves and resistors and wires and magnets, the components that could coax electrons to do your bidding. This visually beautiful potpourri of glass and ceramic and metal could be made to do something that sounds very simple, something that was at the heart of every television set until the 1990s. It could make a beam of electrons and then bend it; and if you do that right, you can make moving pictures.

Jack learned about “CRT” televisions, and I love that name because it connects us to the world that existed before electrons had even been discovered. CRT stands for cathode ray tube, and cathode rays were distinctly odd when they were first discovered. Imagine the early German physicist Johan Hittorf, in 1867, looking at his latest creation. In the gloomy lab, there’s a glass tube with two bits of metal sticking into the space inside at either end, and all the air inside the tube has been removed. This sounds fairly mundane. But imagine how odd it must have been to discover that if you connect a large battery to the two bits of metal, mysterious invisible stuff flowed from one end of the tube to the other. He could tell it was there, because it made the far end of the tube glow, and he could make shadows by putting things in the way. Even though no one knew what was flowing, it needed a name, so it became known as cathode rays. The cathode is the terminal attached to the negative end of a battery, and that’s where the strange stuff was coming from.