# Homework Help: Magnetic force help ?

1. Jul 15, 2008

### thompson.1674

magnetic force help ???

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

In a television set, electrons are accelerated from rest through a potential difference of 23 kV. The electrons then pass through a 0.27 T magnetic field that deflects them to the appropriate spot on the screen. Find the magnitude of the maximum magnetic force that an electron can experience.

2. Relevant equations

.5mv^2
qvbsin=F

3. The attempt at a solution
So this is what i have done but its not right:
23000=.5(9.11E-31)V^2
V=2.247E17
(1.6E-19)(2.247E17)(.27)=.00968 N

But is is not correct.
Can anyone help me out?

2. Jul 15, 2008

### rock.freak667

Re: magnetic force help ???

Kinetic energy=pd*charge of electron.

3. Jul 15, 2008

### alphysicist

Re: magnetic force help ???

Hi thompson,

I don't believe this is correct. For the energy equation, you'll need the potential energy change on the left; do you see what you have instead? Notice that it does not have the right units.

The upper limit on the possible speed would be the speed of light in a vacuum, which is a bit under 3E8 m/s, and so right away you know that can't be correct. That's an important thing to keep in mind when you do problems that involve these huge numbers.

4. Jul 15, 2008

### thompson.1674

Re: magnetic force help ???

okay i see what i did and i have the right answer. thanks for your help