Magnetic flux and emf through a rotating ring

Click For Summary

Homework Help Overview

The problem involves a rotating metal ring in a magnetic field, focusing on calculating magnetic flux and induced electromotive force (emf) as functions of time. The subject area pertains to electromagnetism and rotational dynamics.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the relationship between magnetic flux and emf, with one noting the formula for magnetic flux and its derivative for emf. Questions arise regarding the implications of the ring's rotation about a diameter and the correct application of signs in the equations.

Discussion Status

The discussion is active, with participants clarifying mathematical expressions and questioning the physical setup of the problem. Some guidance has been offered regarding the interpretation of the rotation axis, but no consensus has been reached on the implications of this detail.

Contextual Notes

Participants are navigating potential confusion regarding the rotation of the ring about a diameter and its effect on the calculations. There is also a mention of a possible sign error in the expression for emf.

captainjack2000
Messages
96
Reaction score
0
 
Physics news on Phys.org
Sorry I don't quite know how that happened!
Any way the question is
"A metal ring of radius R rotates with constant angular velocity about a diameter. Perpendicular to the rotation axis is a constant magnetic field B. Calculate as functions of time
a) magnetic flux through ring
b) emf induced

I know magnetic flux = BAcoswt
so emf = -magnetic flux/dt = ABwsinwt
 
arent you missing a minus sign in your final answer?
 
emf = -dphi/dt = -d/dt(BAcoswt) = -(-BAwsinwt) = ABwsinwt
i think
I am a bit confused by the fact that they say "about a diameter" how does this change things?
 
ok. yeah my bad with the minus. the diameter bit just tells you the way its rotating its not rotating about the surface normal but rather like a dynamo would.
 

Similar threads

Undergrad Motional EMF in Faraday disc, co-rotating magnet axial mean flux
  • · Replies 5 ·
Replies
5
Views
1K
Relationship between magnetic field lines and magnetic field
  • · Replies 4 ·
Replies
4
Views
2K
On the magnetic dipole radiation in Griffith's book
  • · Replies 1 ·
Replies
1
Views
2K
What is the Magnetic Flux of a White Dwarf Derived from the Sun?
  • · Replies 3 ·
Replies
3
Views
2K
EMF induced by a magnet falling through a coil
  • · Replies 4 ·
Replies
4
Views
3K
High School Understanding magnetic flux change during the falling of magnet
  • · Replies 1 ·
Replies
1
Views
2K
Flux through a ring due to two charges
  • · Replies 10 ·
Replies
10
Views
1K
How to measure the magnetic field/ induced fem in a system
  • · Replies 2 ·
Replies
2
Views
2K
Rotating and tilting charged disk induces a voltage inside a ring
  • · Replies 11 ·
Replies
11
Views
3K
High School Not sure about the magnetic flux (phi) depending on a cosine function
  • · Replies 9 ·
Replies
9
Views
2K