Once inside the camera, the path of the electrons would split, some shuffling into the computer and some into the camera itself. And the thing about electrical circuits is that in the end all roads lead to Rome, or in this case, back to the battery. The massive yellow buoy was just the skeleton for this branching flow of electrons, and the electrons themselves were generating electric and magnetic fields, pushing and pulling on camera shutters, acting as timers, generating bursts of light and recording data in a huge, intricate synchronized sequence, before shuffling back to the battery.
And all of that was happening while the buoy was being shoved around by the huge waves (25–30 feet high in some cases) of an Atlantic storm. We bobbed about on the research ship and waited, living a life where gravity was an uncertain friend and a tenuous grasp on order was maintained only by imprisoning things with Velcro or elastic bungees or rope. After three or four days, the chemical reaction in the battery had finished—it was back in its original uncharged state. There was no more stored energy left, the electrons could not be pushed around the circuits, and the dance was over. The buoy went back to being an inanimate shell of metal and plastic and semiconductors. But the data had been stored in solid state computer memory, and it was safe.
A few days later, when the storm was over, we tracked the buoy down and hauled it back on board. I’m always extremely impressed by the skill of research ship crews at fishing things out of the water. Ships don’t move sideways, and they’re slow to turn around or change direction. To stand a chance of getting the buoy back, the captain had to bring his 250-foot vessel right alongside it, managing both to avoid running it over and to get close enough for the bosun to reach over and catch it with a long boat-hook. And they usually succeeded on the first try.
Then it was our turn again. The batteries were plugged into the ship’s power supply, providing the energy to push the chemical reactions back the other way ready for the next deployment. The experiments were detached and brought inside, with the exception of the camera. This got left outside in the freezing cold, because the dance of the electrons has a downside, and my poor PhD student was about to pay the price for it.
Possibly the most fundamental physical law we know of, one that has been shown to be accurate time and time again and has never been disproved, is that of conservation of energy. It states that energy can never be created or destroyed, but only shifted around from one form to another. The battery had chemical energy, and the chemical reactions converted that to electrical energy, and then somewhere between one terminal of the battery and the other one, that energy moved on. But where did it go? Things happened—the camera took pictures, the computer programs ran, and data were recorded. But none of that stored the electrical energy in a new place. The energy just leached away, unnoticed. There is a price to be paid for moving electrons around, and it’s the generation of heat. Any electrical resistance inflicts an energy tax on the electrical energy moving through it. Even though the electrons will pick the path of least resistance, some tax must still be paid.?
The camera was housed in thick plastic, a material that transmits heat very badly. When the camera was running, all the energy of the electrons was eventually converted to heat as they flowed around the system. That didn’t matter in the water, because the ocean where we were was about 45°F and stole the heat away, cooling the housing efficiently. But air isn’t up to that task. In the lab, when the computer was running to download the data, the camera kept overheating. We did our best, but the only solution we found was to leave it outside in a bucket of iced water (helpfully, the ship had an ice machine), and so my PhD student had to spend nine or ten hours starting and stopping the downloads to keep the data flowing while preventing the camera from cooking itself. Such is the glamour of field science.
This is why laptops, vacuum cleaners, and hair dryers heat up as you use them. The electrical energy must go somewhere, and if it’s not converted into other kinds of energy, heat is the inevitable end. Hair dryers use this to heat air; their circuits are arranged to dump energy as heat in a very concentrated way. But laptop manufacturers hate heat, because hotter circuits work less efficiently. There is no way of using electrical energy without paying a heat tax.#
So the electrons flow because an electric field is pushing on them. A battery doesn’t really provide electrons—there are plenty of those in the world. What it does is provide the electric field to move electrons. And if the circuit is complete, this electric field will push electrons around the loop. So far, so simple. But what are all those numbers on plugs and in tiny font on the safety warnings? Perhaps it’s best to take the typical British approach to all problems: Find the cookie tin and put the kettle on.
The most important thing about a tea break is that it involves both tea and a break. Some of my American coworkers never really understood this, and used to bring along work to continue discussing it over tea. But for the British, the act of “putting the kettle on” signifies a change of pace. I’m going to do it now, and in this case my kettle is an electric one that I simply fill with water and plug into the power outlet. My mind is allowed to stop working for a bit, while the kettle gets on with its job.
Pushing down on the switch does one very simple thing. It shifts a bit of metal and thereby slots the last segment of a circuit into place. Now there’s a route through the maze of the kettle, a path made entirely of electrical conductors that electrons can easily travel along. This path is now uninterrupted and it runs from one pin of the plug, through the kettle, and back to the second pin of the plug. In this case, the electric field comes not from a battery, but from a plug socket.
A standard three-pin plug has one long pin at the top. That’s called the ground pin. It’s completely separate from the rest of the circuit. Effectively, it’s doing the job that my car did on those cold snowy mornings—it’s there to provide an escape route if any electrons start to build up in the wrong place (say, on the outside of the kettle). So that’s not part of the path that’s going to power the kettle.