Maximum torque on an electric motor

  • Thread starter Dione
  • Start date
  • #1
1
0

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:

Answers and Replies

  • #2
marcusl
Science Advisor
Gold Member
2,726
387
The torque arises ultimately from the Lorentz forces on the charges moving at velocity v within the wires
[tex]\vec{F}=q\vec{v}\times\vec{B}[/tex].

Look in your text, or in a book like Reitz and Milford, Foundations of Electromagnetic Theory. You'll see that, for a loop or coil, the torque T becomes proportional to coil current I and area A
[tex]\vec{T}=I\vec{A}\times\vec{B}[/tex].
[tex]I \vec{A}[/tex] is defined to be the magnetic moment.
 
Last edited:

Related Threads on Maximum torque on an electric motor

  • Last Post
Replies
3
Views
873
  • Last Post
Replies
2
Views
16K
  • Last Post
Replies
4
Views
943
  • Last Post
Replies
8
Views
14K
  • Last Post
Replies
11
Views
597
Replies
3
Views
5K
  • Last Post
2
Replies
33
Views
1K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
6
Views
1K
Replies
3
Views
7K
Top