# Homework Help: Speed and Direction of Electron orbiting within a Solenoid

1. May 28, 2012

### rodanme

In Fig. 28.8, a view of the solenoid, showing the clockwise sense of the current in the windings, is given. An electron is in circular motion near the center of the solenoid, with an orbital diameter of 3.0 cm. The speed of the electron and the sense of the orbital motion are closest to

The diameter of the solenoid is 4 cm
The diameter of the e- orbiting within the solenoid is 3 cm

2. Relevant equations

r = mv/qb

T= (2*pi*m)/qb

3. The attempt at a solution

Not really sure how to start the problem.
Would I take a conservation of energy approach?
Do I need to try and figure out the B field of the solenoid?

2. May 28, 2012

### omoplata

For the next step, consider that the electron is a charged particle that travels in that B field.

3. May 28, 2012

### rodanme

The Equation for B_solenoid = Mu_0 * I * n

how can I find the current of the solenoid?

4. May 28, 2012

### omoplata

They have to give the current, or they want the answer in terms of the current.

Judging by the problem statement, this looks like an MCQ problem. If so, do you have the answer list?

If not, do you have this figure 28.8?