Why is the magnetic field stronger at this specific point?

Click For Summary

Discussion Overview

The discussion revolves around the phenomenon of induced electromotive force (EMF) in a rotating rod within a magnetic field, specifically addressing why the EMF is greater at a certain point (R) compared to another point (P). The scope includes theoretical explanations and mathematical reasoning related to electromagnetic induction.

Discussion Character

  • Exploratory, Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant asserts that the induced EMF is larger at point R due to the larger area of the enclosed circuit, emphasizing that the magnetic field remains constant.
  • Another participant reiterates the claim about the larger area leading to a larger EMF and requests a more detailed explanation of the reasoning.
  • A third participant provides a mathematical expression for EMF, stating that it is influenced by the velocity of charges and the length of the path of integration, noting that both factors increase as one moves further from the origin.

Areas of Agreement / Disagreement

Participants express differing levels of understanding regarding the explanation of the induced EMF, with some agreeing on the factors contributing to the EMF while others seek clarification. The discussion does not reach a consensus on the clarity of the explanation provided.

Contextual Notes

Some assumptions about the system, such as the uniformity of the magnetic field and the nature of the circuit, are not explicitly stated. The discussion also does not resolve the implications of the mathematical expression provided.

selishaphysic
Messages
7
Reaction score
0
A rod (shown in the picture on the link) rotates around the point O in a magnetic field. It is said for sure that the induced EMF in the rod is larger at point R compared to point P. Why's that?

The picture: http://img58.imageshack.us/my.php?image=physicskx4.png
 
Physics news on Phys.org
The EMF is larger because the area of the enclosed circuit is larger. The magnetic field is NOT larger, it is constant.
 
Nick89 said:
The EMF is larger because the area of the enclosed circuit is larger. The magnetic field is NOT larger, it is constant.

Oh I meant the EMF of course. But can you please explain your answer more thoroughly I don't fully understand the situation.
 
The EMF is given by:
\epsilon = \oint \left( \textbf{v} \times \textbf{B}\right) \cdot d\textbf{l}
Here, B is the magnetic field, dl is a small segment of a circuit, and v is the velocity of a charge in that circuit.

If you think of the electrons in the rotating rod as charges going around in a circular circuit, then you can easily see why the EMF is larger when you get further from the origin.
First of all, the velocity v is larger, secondly the path of integration (the length of the loop) is larger.
 

Similar threads

High School Experiment issues (electromagnetism)
  • · Replies 42 ·
2
Replies
42
Views
3K
Undergrad Induced electric fields and induced magnetic fields confusion
  • · Replies 9 ·
Replies
9
Views
4K
High School Force Exerted on a Conductor by a Homogeneous Magnetic Field
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Pushing a rod in a magnetic field
  • · Replies 15 ·
Replies
15
Views
3K
High School Magnet inside a solenoid with current
  • · Replies 7 ·
Replies
7
Views
2K
Undergrad Charge movement relative to magnetic field frame dependence/invariance
  • · Replies 5 ·
Replies
5
Views
2K
Undergrad Average Magnetic Field Between 2 Conducting Rods
  • · Replies 1 ·
Replies
1
Views
1K
Undergrad Magnetic field at a point along the solenoid's axis but outside the solenoid
  • · Replies 5 ·
Replies
5
Views
2K
High School Seeing both B field lines and E field lines at the same time
  • · Replies 22 ·
Replies
22
Views
2K
High School Confusing diagram of a rotating coil in a magnetic field
  • · Replies 4 ·
Replies
4
Views
2K