# Homework Help: Dropping a closed loop into a magbetic field

1. Nov 15, 2012

### sgstudent

1. The problem statement, all variables and given/known data
The closed loop is vertical and the magnetic field is a north and south pole such that the looped end faces the magnetic poles.

A multiple choice question answer stated that the closed loop will have a smaller acceleration than 10mls

^2 as it would experience an opposing force. But if I look at it closely, won't the 2 induced force cancel each other so it will accelerate at 10m/s^2?

2. Relevant equations
None

3. The attempt at a solution
My explanation goes like this: when it is dropped into the magnetic field, it experiences a change in magnetic flux linkage and thus there would be a current induced induced it. since there is a current flowing perpendicular to the magnetic field, by Fleming left hand rule there will be 2 forces acting on the closed loops at the two edges there are equal and opposite. Hence, this cancels out the force which allows the downwards acceleration to be still 10m/s^2.

Is there something wrong with my concept here? It seems correct to me though. I hope you guys can answer me as soon as possible cos tomorrow is my physics O level paper thanks for the help!

2. Nov 15, 2012

### bsbs

do you have the answer since it's a MCQ?

Lenz's law?

3. Nov 15, 2012

### sgstudent

The answer is that the acceleration is less than 10m/s^2. But since they cancel out so shouldn't it be 10m/s^2?

4. Nov 15, 2012

### bsbs

Read about lenz's law about opposing induced force. It satisfied the answer and in actual fact, they do not cancel out.

5. Nov 16, 2012

### sgstudent

Why won't they cancel out? Since the current is the same at both ends?