# Maximum torque on an electric motor

## 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 = µ0(N/L)I/sqrt (1 + (2R/L)2)

µ0 = 1.257e-6 N*s2/C2

## 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

Last edited by a moderator:

Related Introductory Physics Homework Help News on Phys.org
marcusl
$$\vec{F}=q\vec{v}\times\vec{B}$$.
$$\vec{T}=I\vec{A}\times\vec{B}$$.
$$I \vec{A}$$ is defined to be the magnetic moment.