# Homework Help: Magnetic Fields of electron

1. Mar 25, 2007

### AznBoi

1. The problem statement, all variables and given/known data
An electron is accelerated through 2400V from rest and then enters a region where there is a uniform 1.7 T magnetic field. What are (a) the maximum and (b) the minimum magnitudes of the magnetic force acting on this electron?

2. Relevant equations
$$F_{b}=q(v * B)$$

3. The attempt at a solution
I'm unsure of where to start. How do you calculate the speed (v) if they only give you the voltage that the electron goes through? I have all of the other required information to plug in the equation but not the speed of the electron. Thanks.

2. Mar 25, 2007

### AznBoi

Here is another problem in which I cannot find the velocity of the particle:
A singly charged positive ion has a mass of 2.50 x 10^-26 kg. After being accelerated through a potential difference of 250V, the ion enters a magnetic field of 0.500 T, in a direction perpendicular to the field. Calculate the radius of the path of the ion in the field.

How do you find the velocity of the ion given the potential difference it travels through? I know how to solve the rest of the problem but I'm just stuck on the speed (v) of the particle.

3. Mar 25, 2007

### Mentz114

You can get the velocity of the electron by calculating the kinetic energy it gains in the field. The rest mass of the electron is well known but I can't remember it.

Same for the second question but a different energy and mass involved.