What's a plausible way prove the existence of the “electron” to the doubters? [closed]

Question

So, at many colleges in the North American region, most famously the New Jerusalem University and Chicago Collegium, much old world, pre-apocalyptic information is often taught at schools, including the electron and electricity. Old electrical engineering books and warning labels translated to New English is what college kids are taught from. But there is a huge feud going on in the academic community about the electron and electricity.

Believers, called “electricians”, say that many pre-apocalyptic books and other materials cite the electron and electricity as real, concrete facts. They also claim that technology of the old world was impossible without electricity.

Doubters, called “anti-electricians”, say that it is highly plausible that old time books were mistranslated, and that besides the books, they have no real proof of the electron. The also say that it is possible that Old world technology was powered by some other source, possibly witchcraft, and that teachings of the electron should be taken out of school.

So, here is my question: How could the believers plausibly prove to the doubters that electrons and electricity are real?

Answer 1

Electricity is easy. Shuffle-shuffle-touch-OW! That's electricity, baby...

Proving the electron is a bit more complicated, but borrowing from this question and its answer from our sister site, physics.SE, we find the Millikan Oil Drop experiement.

Basically, oil droplets were allowed to fall between two metal plates with an electric field (thousands of volts, don't try this at home) between them. The result is that as the voltage was changed, the particles would move up and down. The result of the analysis is the ability to mathematically and empirically determine the charge of an electron.

Which you can only do if it exists, of course.

Rubbing a baloon on your head is more fun, though. So is rubbing a cat with a glass rod and touching your friend. Proving the existence of electricity is so trivial that it's hard to believe the existence of the argument — unless they don't have access to electricity and don't want to follow in Ben Franklin's footsteps with a kite, a key, and a convenient thunderstorm.

Answer 2

Competing theories

As other people have pointed out, electrical phenomena are so commonplace it would be irrational for a scholar to ignore what a piece of fur and a glass stick can show you. Proving that electrical phenomena are the result of the mutual attraction or repulsion of tiny, indivisible charged particles is a much harder endeavor; it would probably take more than one experiment to convince the 'anti-electricians' that electrons are real. Furthermore, you might still be skeptical that electrical phenomena are powerful enough to have powered the machines of the past.

Here's how I would do it, given a weekend with a room full of doubters, and a prepared laboratory full of 1700-1800 tech:

1) Two Types of Charges

Using a variety of triboelectric materials (fur and glass rod, plastic and felt, etc.) I would then take turns transferring the charge (by touch) to some suspended metal spheres: If we take the fur and glass rod as an example, there are three possibilities:

1. I touch the fur to both metal spheres independently. In this case the two spheres repel.
2. I touch the glass to both metal spheres independently. In this case they still repel.
3. I touch the glass to one sphere and the fur to the other. In this case they attract.

From this, and repeating the experiment for different materials, I make the hypothesis there are are only two types of charges, and similar charges repel while opposites attract. Note this says nothing about charges being discrete; I have yet to show that the presence of 'positive' and 'negative' charge isn't fluid-like (i.e. it's a continuous substance with no 'smallest amount').

2) Crooke's Tube

After demonstrating the rubbing of glass on fur or felt and plastic can separate charges, I would demonstrate a machine that takes that process and repeats it continuously: The Wimhurst machine depicted above is a hand-powered, high-voltage generator. A Van de Graaff generator would also prove sufficient for this purpose. After repeating the same experiments as in part 1), I would then connect the generator to a partially evacuated glass tube with a single metal surface on the inside as shown:

The metal plate, called the cathode, is present in the back of the tube, while the second metal connector is placed elsewhere (the bottom in this case). The cross in this picture is electrically isolated. When the generator is cranked, cathode rays emanate and project a shadow. The presence of the shadow clearly indicates that something is leaving the cathode, traveling in straight lines, and striking the wall of the tube. This helps confirm that when there is indeed a transfer of some sort of electric material during electric phenomena, as opposed to being imbued with an 'electric property'.
As a bonus, placing an electrically charged sphere next to the tube will deflect the cathode rays, confirming their electric nature.

3) Millikan Oil Drop Experiment

Once you have demonstrated that only two charges exist, and that an actual substance is responsible for electricity, the nail in the coffin is of course the oil drop experiment performed by Harvey Fletcher and Robert Millikan in 1906. I think the experiment could have been performed with earlier technology; perhaps in this society the necessary parts could be scavenged instead of manufactured. Here is a diagram of the experiment: This is a statistical experiment: as oil droplets enter into the chamber, they receive a small net electric charge. By varying the charge applied to the plates, you should be able to apply the correct electric attractive force to suspend the small oil drop against the pull of gravity. This allows you to calculate the suspending force from the plates. What Fletcher and Millikan noted was that the force is always some integer multiple. That indicates that the amount of charge present is discrete, which the fluidic / aetheric models of electricity cannot account for. With a bit more math and a calculation of the mass of the oil droplet, you can work out the charge on the electron. Although that is not strictly necessary if all you care about is showing the discrete nature of the electric charge.

Answer 3

I will point out that in today's electrical engineering we pretty much do this. Albeit not with the neo-luddite trappings. We generally think in terms of volts and amperes flowing from the positive to the negative, and never about the electrons* - that's physicist territory. And why not? Most of the time the fiddling small details of electrons don't matter in electronics.

To demonstrate the existence of electrons you need to prove they're practically useful to have as part of your world model. For this you want to call in the chemists, who deal with electrons in a more direct fashion. A few rounds of demonstration starting with the famous lemon battery should suffice: different metals and electrolytes will have different results that can be predicted based on their valency, ultimately reconstructing a car battery from first principles.

The reason we want a chemist is because we want someone qualified to predict what happens when we arbitrarily vary the conditions. This then becomes the foundation of our proof: if electrons didn't exist, we wouldn't be able to predict what happens with different substances based on the properties of their electrons (amongst others). Since we can, we can disprove the non-existence of electrons.

*This is called 'Conventional Current'. In reality the electrons flow from negative to positive but it has the same result so nobody cares.

Answer 4

Van de Graaff generator

Take a glass rod and a piece of silk, or a piece of amber and some fur (arguably the better post-apocalyptic choice). Rub the two together vigorously for perhaps 10 or 20 seconds - I've found 10 is often enough. Congratulations! You've transferred charge. More importantly, you can do things with this charge. It's not hard to make a tabletop Van de Graaff generator (here's one in action), which uses a similar mechanism to transfer charge to a metal sphere. If you take a second metal sphere and hold it close enough . . . you get a spark! It's quite a dramatic demonstration, even on a small scale.

^{A small Van de Graaff generator. Image courtesy of Wikipedia user Lefrancq under the Creative Commons Attribution-Share Alike 3.0 Unported license.}

Going back to the amber and fur (which, by the way, might be mentioned in one of those apocryphal books), it's clear that something has to be transferred, right - some sort of charge. That's where the electron comes in. Define an electron as simply a particle that carries charge - or even just say that it's a little bit of charge. The small sparks that you can generate should convince people that there is indeed such an object.

Helmholtz coils

Another possibility - one I like even better - involves using Helmholtz coils. Helmholtz coils are pairs of circular bunches of wire, each bunch having a large number of loops, separated by a distance on the order of the diameter of the wires. When a current is passed through the wires, a simple magnetic field is created between the coils, which is uniform midway between the two. If you fill a chamber with the right kind of gas - I've used helium - and find a way to eject electrons into the chamber at the right angle, placing the chamber inside the coils, the electrons will follow a circular path, colliding and exciting helium atoms, making them emit light. It's pretty dramatic.

The only issue, of course, is that Helmholtz coils are powered by electricity, which you clearly don't have. Therefore, if you can either power the coils by hand somehow (unlikely) or generate a uniform magnetic field from one or more permanent magnets, this can work - and it will probably convince the doubters even more, since they can see the path of the electrons.

Here's what the apparatus looks like, from the side:

^{Image from my a lab manual at my college. Image credit Adam Light.}

---

It's been argued that these experiments merely show that there exists some substance or fluid with electric charge. It's not hard to construct an argument that there must be some small components of that fluid - after all, you can make the same argument for atoms via Brownian motion using nothing more than a minimal microscope. If normal fluids are made up of small particles, why shouldn't this "electrical fluid"?

Answer 5

Showing that there is a force, and it can be harnessed to do useful work, is easy. You just need a bog-standard dynamo with a crank, an electric motor, and some wires to connect them. Even if you don't have batteries to store power, this rig will let you demonstrate that motive force is being transferred in some form that's clearly not mechanical (the wiring doesn't move, and wouldn't be large or strong enough to carry that much force even if it did).

That doesn't prove any of the other properties of the electron, or that it's what the ancients based their technology on, but it's clear evidence of something happening.

Answer 6

Batteries!

Batteries were the first reliable source of electricity, and perhaps date back to ancient times. You can with some effort, generate a stack of plates to produce a substantial voltage, enough for an arc. Proof of electricity follows simply from using wires to conduct your charge to wherever you want.

Proof of the electron is more difficult. Historically electricity was viewed by some as a fluid. As pointed out above, chemistry is a good way to show that there is something integral going on since reactions occur in stoichiometric proportions. Again, the Millikan oil drop experiment was the first clean demonstration of the quantized nature of charge.

Answer 7

Thomson's experiments established the identity of electrons:

He found that the mass-to-charge ratio was over a thousand times lower than that of a hydrogen ion (H+), suggesting either that the particles were very light and/or very highly charged. Significantly, the rays from every cathode yielded the same mass-to-charge ratio. This is in contrast to anode rays (now known to arise from positive ions emitted by the anode), where the mass-to-charge ratio varies from anode-to-anode.

The existence of cathode and anode rays, along with the material-independence of cathode rays proves there's some charge carrier common to all materials used.

https://en.wikipedia.org/wiki/J._J._Thomson#Measurement_of_mass-to-charge_ratio

To build up the hard vacuum needed for cathode rays, you'll need some glassware and mercury.

https://en.wikipedia.org/wiki/Sprengel_pump

https://en.wikipedia.org/wiki/McLeod_gauge

To power the apparatus we'll want reliable power, with major options being electrolytic cells and your choice of generator.

So far we need:

• a good deal of copper drawn into wires;

• glassblowing (making narrow-bore capillary glass may be a challenge);

• metallic mercury; and

• an electrical power source, most likely one of:

  • metals and concentrated acid for battery chemistry or

  • magnets, frame, and bearing for a dynamo.

What, you want precision measurement, too? Of course you do. For expediency, I'll just point out that it's possible, if not common, to boostrap your way with precision surfaces.

https://en.wikipedia.org/wiki/Surface_plate#History

Thus far, the outside materials we need were more or less known by the medieval period. We should also call for some abrasives - maybe we luck out and can get low-grade sapphire. More modern steelmaking processes would also be nice, and we might end up asking for refined platinum or tungsten as part of tooling and our vacuum tubes.

As an alternative to isolating electrons themselves, we could focus on crude semiconductors. With wire, galena, and a very fine-point conductor (we probably need high-quality steel here), we can start work on RF experiments, AM, and a detector.

I'm not sure where to put this, but with a rectifier we can more assuredly get the Thomson experiments working since any generator design would be usable as a DC source. It's as good as done if you can isolate, say, cadmium and selenium. https://en.wikipedia.org/wiki/Metal_rectifier

Incidentally, you would very likely need to remove all electrical artifacts and if not all human memory to 'lose' awareness of electrons as real entities.