# Magnetic Force on an Electron

1. Jul 25, 2007

### kiwikahuna

1. The problem statement, all variables and given/known data
An electron in a vacuum is first accelerated by a voltage of 48200 V and then enters a region in which there is a uniform magnetic field of 0.183 T at right angles to the direction of the electron's motion. What is the force on the electron due to the magnetic field?

2. Relevant equations

F = qvBsintheta

3. The attempt at a solution

U = Vq (potential energy)
1/2 mv^2 (kinetic energy)
I set potential energy equal to kinetic energy to solve for velocity.

Vq = 1/2 mv^2 (then solve for v)
v = SQRT(2qv/m)

F = qB(SQRT(2qv/m))sintheta
Plugging in the numbers, I get
F = (1.6e-19) (0.183T) (SQRT(2(1.6e-19)*48200V/9.11e-31))* sin (90)
F = 3.82 e -12

Is this the right way to do this problem? Thanks in advance for looking it over for me.

2. Jul 25, 2007

### G01

You seem to be correct as long as the electron starts off at a velocity of 0, which I'm assuming it does since the problem does not state otherwise. I also get the same answer that you do. Nice job!