# Homework Help: Electrons in a uniform electric field.

1. May 8, 2007

### lord_blurg

1. The problem statement, all variables and given/known data

Basically, I am writing up a practical experiment dealing with Electrons in a uniform electric field (I.e. Using an electron gun).

There are two parallel plates, one with a positive charge and one with a negative charge. Between these to plates is a grid which allows for easy graphing.

It can be assumed that the electric field between the plates is uniform. A grid (with lines seperated by 1 cm) is shown. I need to use this information to determine the distance, d, between the plates and to calculate the strength of the uniform electric field, E.

How do I find out the distance between the 2 parallel plates? (Probably simplistic, it's just that I am doing this experiment based on an experiment video I watched)

The anode voltage is set to 3,000 volts.
The graph I got was y=(.0504)(x)^1.763

2. Relevant equations

I am assuming this equation is related...

E = V/d (V is the potential difference between the plates.)

2. May 8, 2007

### Weimin

Theoretically, the equation is y=(a/2/v^2)x^2

where, a is the acceleration=eE/m
v is the initial velocity, assumed to be parallel to the plates

If you substitute all these quantities to above equation then
y=eE/(2mv^2)x^2

and while mv^2/2=eV with V is the voltage

y=(E/4V)x^2

You do not need the distance between 2 plates.

Here you got the power of about 1.7<2. Hmm, was the experiment held in vacuum or in some gas?