# Homework Help: Help with magnetic induction and finding induced current

Tags:
1. Apr 6, 2016

### mick5000x

1. The problem statement, all variables and given/known data
I have attached a picture that details the problem. This is my practice test and I have no clue what I am doing wrong. Essentially a loop of wire is moving in constant velocity into a magnetic field. The magnetic field lines are pointing into the page. The problem is asking which at which points is the loop's induced current flowing clockwise and counterclockwise. I do not need the answer for 14 and 15.

2. Relevant equations
Lenz Law
Right Hand Rule

3. The attempt at a solution
I attempted to use right hand rule, where my thumb points in the direction of the current. I figured out that if you point your thumb in the counterclockwise direction current of B, it will give you an upward magnetic field inside the loop, which is exactly what I wanted. However, I cannot figure out why D is moving in the clockwise position because if I try the right hand rule, it will point inside the loop, the same direction as the magnetic field.

File size:
15.7 KB
Views:
122
2. Apr 6, 2016

### TSny

Welcome to PF!

Is the magnetic flux through the loop increasing or decreasing at D?

3. Apr 6, 2016

### mick5000x

Thanks for the welcome! Isn't the magnetic field constant throughout, meaning the magnetic flux is constant? Or does magnetic flux decreases along the X axis even though magnetic field is constant?

4. Apr 6, 2016

### TSny

How would you determine the magnetic flux through the loop at the instant when the loop is at D?

5. Apr 6, 2016

### mick5000x

From what I understand, magnetic flux is equal to B * A, where B is the magnetic field that is perpendicular to the surface, and A is the surface area. Does this mean the change in magnetic flux between the two halves of D causes magnetic flux to decrease?

6. Apr 6, 2016

### TSny

When using Φ = BA at point D, the area A is the area inside the loop where B is nonzero. The region where B = 0 inside the loop does not contribute to the magnetic flux through the loop.