# Homework Help: Various Faradays Law Questions

1. Jan 17, 2012

### jegues

1. The problem statement, all variables and given/known data

See the figures attached for each of the individual problem statements.

2. Relevant equations

3. The attempt at a solution

I'll start by explaining my concerns for each problem,

P1) Did I plot the Iinduced waveform correctly? I'm having some trouble picturing what the waveform of the magnetic flux would be, it seems to me as the current would increase as the flux increases so it should follow from the current waveform somewhat, correct?

P2) Is my expression for Vemf(t) correct? Is the expression I wrote down for the average power delivered to the load resistor correct?

P3) Again, I'm not sure if I've done this problem correctly, can someone check my results?

Thanks again!

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2. Jan 17, 2012

### technician

The falling magnet means that the loop experiences a changing magnetic flux so an emf will be induced which will give rise to an induced current in the loop.
The induced emf (and current) will oppose the change producing it (Lenz's law) which means that as the N pole approaches the loop the current will be in a direction to create a N pole (that is a current direction opposite to the direction you have drawn)
As the N pole leaves the loop the induced emf and current will change direction to produce an S pole of the loop
As the S pole approaches the loop the induced current will again oppose the change which will produce a S pole again from the loop.... same current direction.
As the S pole leaves the loop the induced emf and current will be in a direction to create a N pole from the loop.
I think the curve should be 2 'pulses' going +ve...-ve....-ve....+ve

3. Jan 17, 2012

### jegues

So basically I've mixed the direction of the currents up as the magnet passes through the loop?

4. Jan 18, 2012

### jegues

Bump, still looking for verification on the other questions.