Toruq on a current loop

  • Thread starter vg19
  • Start date
  • #1
67
0
Hey. Ive read in my text that the netforce acting on a current loop in a uniform magnetic field is zero. But, in the next section, it mentions how torque is exterted on a loop placed in a uniform magnetic field. How can this be if the netforce must be zero? (I think Im making a really simple error here)
 

Answers and Replies

  • #2
Physics Monkey
Science Advisor
Homework Helper
1,363
34
Hi vg19,

The net force in a uniform field will be zero, but the torque doesn't have to be. Imagine, for example, a square current loop in the yz plane with the magnetic field along the z axis. The current in the loop flows counter-clockwise when viewed from the positive x axis. In other words, the current in the bottom part of the wire is in the positive y direction, and the current in the top part of the wire is in the negative y direction. Hopefully you can visual my scenario despite the poor description. The force on the sides of the wire are zero because the current there is parallel to the field. The force on the top of the wire is in the negative x direction while the force on the bottom of the wire is in the positive x direction. These forces have equal magnitude and point in opposite directions as they must. Now what about the torques? So this is my question to you, do the torques exerted by these forces add up or cancel out?
 
Last edited:
  • #3
67
0
Ahhh the torques WILL add up but the netforce will be zero since one will be pointing up and one down.

I totally get it!

Thanks a lot!
 
  • #4
Physics Monkey
Science Advisor
Homework Helper
1,363
34
Glad I could help.
 

Related Threads on Toruq on a current loop

  • Last Post
Replies
2
Views
1K
  • Last Post
Replies
0
Views
5K
  • Last Post
Replies
8
Views
1K
  • Last Post
Replies
3
Views
7K
  • Last Post
Replies
4
Views
3K
  • Last Post
Replies
5
Views
10K
  • Last Post
Replies
2
Views
9K
Replies
0
Views
4K
Replies
3
Views
21K
  • Last Post
Replies
11
Views
8K
Top