Tuesday, May 26, 2009

The weight of an electron

One of the main experiments to determine the weight of an electron in an educational physics class involves balancing a metal beam partially inside a solenoid (inductor – a big cork screw of tightly wrapped wire). The problem with this is that the force applied by the solenoid is dependent on the type and orientation of the metal balance beam inside core of the solenoid.

The other main way to measure the weight of the electron is by Thompson's charge-to-mass ratio experiment.

Picture provided courtesy of NYU website.

The inductors (solenoids) let off a gradient magnetic field which will affect the path of the electron throughout its journey through the experimental apparatus - it can be very difficult to eliminate fringe fields from a solenoid. This makes an accurate model of the electromagnetic forces on this electron difficult to model mathematically.