Induced current in a coil from a constant uniform magnetic field?

  • #1
greg_rack
Gold Member
363
79
Assume a solenoid coil(made up of ##N## windings) placed in the horizontal(##\hat{y}##) direction and in a constant uniform magnetic field.

Would an induced current run through the(closed) coil if it spins around its central horizontal ##\hat{y}## axis? My guess is "no", since such a current is generated only when a magnetic flux variation occurs(Faraday-Neumann law), and in this case, the flux through the coil stays exactly the same... but my textbook is quite confusing in this passage.

I anticipate your response(s) with another question:
- if the answer of the above is actually "no", then, how can a current be generated in the solenoid? Again, my guess is that in order to do so it should rotate around its vertical ##\hat{z}##(according to the reference chosen before) axis, causing an area and flux variation accordingly.
 
Physics news on Phys.org
  • #2
greg_rack said:
Summary:: An ambiguous statement in my textbook gave me such a doubt

My guess is "no", since such a current is generated only when a magnetic flux variation occurs(Faraday-Neumann law),

If the motion of the core windings moves through field lines, a current will be generated.
There's no difference between moving windings or a moving magnetic field
The only requirement is that by either process, the windings move through (cross) field lines
 
Last edited:
  • Like
Likes greg_rack
  • #3
davenn said:
If the motion of the core windings moves through field lines, a current will be generated.
There's no difference between moving windings or a moving magnetic field
The only requirement is that by either process, the windings move through (cross) field lines
I don't think that is the question. If I understand, the solenoid is being spun axially (say y) in a field always perpendicular (say z) to that axis. So the answer is no. Except there will be a small effect depending upon how you "close" the helix back to the beginning.
 
  • Like
Likes greg_rack
  • #4
hutchphd said:
I don't think that is the question. If I understand, the solenoid is being spun axially (say y) in a field always perpendicular (say z) to that axis. So the answer is no. Except there will be a small effect depending upon how you "close" the helix back to the beginning.
Reading his Q, he seemed to have an overall confusion on when a current is generated or isnt

I have given him the why or why not, he can then apply that to his situation and then determine if
field lines are being cut or not and he will have his answer for his example :wink:
 
  • Like
Likes hutchphd
  • #5
greg_rack said:
how can a current be generated in the solenoid?
Per Faraday's Law, you need the amount of magnetic flux piercing the plane of the coils in the solenoid to be changing.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html

1610485512935.png
 
  • Like
Likes greg_rack
  • #6
Thanks guys!
 
  • Like
Likes hutchphd and berkeman

Similar threads

Replies
6
Views
752
Replies
42
Views
695
Replies
43
Views
5K
Replies
16
Views
3K
Back
Top