Posted by **J** on Monday, February 25, 2008 at 5:27pm.

A beam of protons is accelerated through a potential difference of 0.745 kV and then enters a uniform magnetic field traveling perpendicular to the field. (a) What magnitude of field is needed to bend these protons in a circular arc of diameter 1.75 m? (b) What magnetic field would be needed to produce a path with the same diameter if the particles were electrons haveing the same speed as the protons?

ok for part (a) I confused on what equation to incorporate all the givens! I am lost! and for part (b) you would just need to change the mass of the the protons to the mass of electrons or is there more to that?

- Physics -
**Damon**, Monday, February 25, 2008 at 6:16pm
The kinetic energy of the proton is (1/2) m v^2

Therefore (1/2) m v^2 = 745 volts * charge of proton

That gives you v, the speed of the proton.

Now use your force on a particle in a magnetic field to get the radius of path (if you do not have the equation in your book) If you do, just skip to the end of the next paragraph.

F = q v B if B perpendicular to v

= mass * centripetal acceleration = m v^2 /R.

So R = m v /(q B)

That is all you need.

In part B m changed for the proton. That changes the velocity from (1/2) m v^2

and also makes a change in the radius equation.

(1/2) m v^2 = q V

v = sqrt (2 q V/m)

then for th radius

R = m v/(qB) = sqrt(2 q V m)/(q B)

so the radius goes up with sqrt(m)

of course the sign of q changed, but that only changes the direction, not the radius.

## Answer This Question

## Related Questions

- Electromagnetism - A particle with a mass of 6.64x10^-27 kg and a charge of +3....
- Physics - An á-particle has a charge of +2e and a mass of 6.64 10-27 kg. It is ...
- Physics - An -particle has a charge of +2e and a mass of 6.64 10-27 kg. It is ...
- physics - speed of electron in magnetic field - A beam of electron is ...
- Physics - An electron beam of a TV picture tube is accelerated through a ...
- Physics - A singly charged positive ion has a mass of 2.74 10-26 kg. After being...
- physics - The picture tube in an old black-and-white television uses magnetic ...
- Physics - A singly charged positive ion has a mass of 3.20 10-26 kg. After being...
- PHYSICS - A particle with a mass of 2.00x10-16 kg and a charge of 22.0 nC starts...
- physics - In earlier learning sequences we described how a static magnetic field...

More Related Questions