Proof of electrons.

[Ryanel]

I've recently been looking at electrons and electricity at school. What I have wondered is how people know they're there at all? It's not that I don't believe that they're actually there, it's more that I want to understand how we know.

If anyone could enlighten me, that would be absolutely brilliant!

 

Edward.

[Sensei]

Build your own Cloud Chamber (cost $20-50 for dry ice model), and see their traces on your own eyes..

If you will place magnet/electromagnet below/inside of chamber, particles with negative charge (such as electron, muon-, pion-, kaon-, antiproton) will "curl" in one direction, while particles with positive charge (alpha, proton, positron, pion+, kaon+) in opposite direction.

Radius of curl will reveal mass and momentum of particle.

Edited August 26, 2014 by Sensei

[swansont]

We know there is charge and the Millikan oil drop experiment shows that the charge is quantized. Deflection of a beam of electrons in a magnetic or electric field (as Sensei points out) shows that they have a small mass.

[Enthalpy]

In electronics, individual electrons are often observed directly.

 

For instance at sensitive cameras, where the collected charge is multiple of q.

Or in small MOS transistors, where the noise voltage is multiple of q/C where C is the grid capacitance.

 

Less direct: noise amplitude depends on charges being a multiple of q. Easy to observe as well, for instance the noise voltage of a resistor, the noise current of some current sources.

[swansont]

ALso, of course, people have trapped individual electrons in Penning traps, in order to precisely measure their properties.