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## Homework Statement

In an electric motor, a coil with 200 turns of radius 2 cm can rotate between the poles of a magnet. The magnetic field strength is 0.2 T. When the current through the coil is 50 mA, what is the magnitude of the maximum torque that the motor can deliver?

__Variables__

N = 200 turns

R = 2e

^{-2}m

B = 0.2 T

I = 50e

^{-3}A

τ = ?

## Homework Equations

F = ILB

B = µ

_{0}(N/L)I/sqrt (1 + (2R/L)

^{2})

µ

_{0}= 1.257e

^{-6}N*s

^{2}/C

^{2}

## The Attempt at a Solution

I first wanted to find what the L was so I could solve for the force. So I tried that. That didn't work out too well. I then tried anything. I'm still not sure I entirely understand the concept. I cannot receive credit for the problem even if I get it right anymore, but I'd like to know how to handle this if it pops up on the exam.

http://img48.imageshack.us/img48/1562/electricmotor1oc1.th.jpg [Broken]

Thanks for any and all help,

Dione

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