This question caused a debate in the class: EMF from a changing magnetic field

  • Thread starter Thread starter Physical_Fire
  • Start date Start date
Click For Summary

Homework Help Overview

The discussion revolves around electromagnetic induction, specifically the relationship between electromotive force (EMF) and a changing magnetic field. Participants are debating the correct answer to a question related to EMF induced by a varying magnetic flux.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants are exploring the relevant equations for EMF and magnetic flux, discussing the implications of a graph depicting magnetic flux over time, and questioning the placement of key points on that graph.

Discussion Status

There is an active exchange of ideas regarding the interpretation of the graph and the relationship between magnetic flux and induced EMF. Some participants express confidence in their reasoning, while others seek clarification on specific points. No consensus has been reached yet.

Contextual Notes

Participants are working with a question sourced from the internet, which has led to differing opinions on the correct answer. There is mention of a graph that needs to be accurately labeled to reflect the changing magnetic flux and its effect on EMF.

Physical_Fire
Messages
54
Reaction score
11
Thread moved from the technical forums to the schoolwork forums
Hello,
So recently our class have learnt about E.M.F induction entirely with it's equation and a classmate found a question from the internet. I honestly believe the answer is A as the magnetic field is changing rapidly, but some of my classmates believe it's B. While others believe it's C. This has caused a debate to ensue and I shared my reasoning. What does the community think is the correct answer?
1717688734147.png
 
Physics news on Phys.org
What is the Relevant Equation relating EMF to the magnetic flux through the coil? Can you sketch a plot of the magnetic flux versus time while the magnet is spinning (and label the points P, Q, R on that plot)?

And based on the Relevant Equation, what do you need to do to that plot to show the EMF induced in the coil versus time? :smile:
 
-d phi(b) / change in t. phi(b) is the change in magnetic flux. and the graph would be as attached. However, I am not sure how to label as I don't understand which has the highest emf
1717689686205.png
 
Reply
  • Like
Likes   Reactions: berkeman
Good. The first vertical dotted line on the left is in the wrong place, though, and should be at the Origin (move it to the left).

Where do you think point Q could be on the graph?

EDIT -- the 3 middle points on the 2 graphs look okay, but the outer points are a bit misaligned (the bottom sine wave is asymmetrical)
 
Q should be the second vertical line as it has the magnetic flux is changing rapidly so emf is at its max. So does that mean it's A, and I was secretly right the entire time?
 
Physical_Fire said:
Q should be the second vertical line as it has the magnetic flux is changing rapidly so emf is at its max. So does that mean it's A, and I was secretly right the entire time?
It could be either of the zero crossings of the flux sine wave, so yes, I believe the correct answer is A.
 
Thanks for resolving.
 
Reply
  • Like
Likes   Reactions: berkeman

Similar threads

Motional EMF in the presence of a time-varying magnetic field
  • · Replies 11 ·
Replies
11
Views
3K
Direction and magnitude of electric field produced by current change
  • · Replies 8 ·
Replies
8
Views
1K
Electric field in a rotating rod in a magnetic field
  • · Replies 3 ·
Replies
3
Views
2K
Spring-mediated dipole in a magnetic field
  • · Replies 31 ·
2
Replies
31
Views
2K
How Do You Calculate Terminal Velocity of a Metal Ring in a Magnetic Field?
  • · Replies 3 ·
Replies
3
Views
2K
A magnetic field of 0.0200 T [up] is created in a region....
  • · Replies 5 ·
Replies
5
Views
2K
Calculating the EMF in the coil while the field is changing
  • · Replies 6 ·
Replies
6
Views
2K
Describe the EMF induced by a magnetic field
  • · Replies 2 ·
Replies
2
Views
3K
Magnetic Flux Questions from Japanese University Exam Papers
  • · Replies 7 ·
Replies
7
Views
2K
Powering an LED via Induced Current
  • · Replies 10 ·
Replies
10
Views
4K