Electrons in a beam of televison tube

[Gonger]

Ive got a question where I have to find the acceleration of a single electron due to the magnetic field. Now here is what I did. I tired to find Velocity using KE = .5mv^2. Solving for v. Then knowing that F=qvB and F=ma I made the equation qvb/m=a. But I can't get this to work. Is there some thing that I'm doing wrong. This is a related question with the numbers in it:

Each of the electrons in the beam of a television tube has a kinetic energy of 24.0 keV. The tube is oriented so that the electrons move horizontally from geomagnetic south to geomagnetic north. The vertical component of Earth's magnetic field points down and has a magnitude of 65.0 µT. In what direction will the beam deflect?

I think my problem is with converting uT to T for the electric field. And converting my 24 keV to J. Anyone have some help. Thanks.

 

[Andrew Mason]

Ive got a question where I have to find the acceleration of a single electron due to the magnetic field. Now here is what I did. I tired to find Velocity using KE = .5mv^2. Solving for v. Then knowing that F=qvB and F=ma I made the equation qvb/m=a. But I can't get this to work. Is there some thing that I'm doing wrong.

Your approach is correct except that the force is:

\vec F = q\vec v \times \vec B = qvBsin\theta

What is the angle of \vec v to the magnetic field?\vec B Why not show us what you have done? It is a little hard to figure out where you may have gone wrong otherwise.

AM

 

[witze]

Well, the vertical component of B was given in the problem, so I don't think you need to do the cross product. You're probably just having problems with unit converstions.