# Magnet through Loop (Faraday's Law?)

Magnet through Loop (Faraday's Law??)

A constant magnetic field passes through a single rectangular loop whose dimensions are 0.35 m 0.55 m. The magnetic field has a magnitude of 2.1 T and is inclined at an angle of 50° with respect to the normal to the plane of the loop.
(a) If the magnetic field decreases to zero in a time of 0.40 s, what is the magnitude of the average emf induced in the loop?
(b) If the magnetic field remains constant at its initial value of 2.1 T, what is the magnitude of the rate A / t at which the area should change so that the average emf has the same magnitude as in part (a)?

I used Faraday's Law: emf=-N(change in flux/change in time)

For part (a), I used Faraday's law and plugged in magnetic flux=BAcos50 for the change in flux. The Area and the cosine is the same, so the equation reduced down to emf=-N*A*cos50*(B final-B initial/time).

For area I multiplied the length and width of the rectangular loop. So when I plugged in the numbers into the equation I got emf=-1*0.1925*cos50*(0-2.1/40) and I got the emf to be 0.00649617 Volts. Apparently this wasn't the correct answer when I plugged it in. Am I doing something wrong??

For part (b) I can't get until I get part (a) first. Could you please help me and tell me if I did something wrong. Thanks a lot!!!

## Answers and Replies

mjsd
Homework Helper
firstly, in your question you said 0.40s later you used 40 in your equation.... which is correct?

Yeah your right, sorry about that, guess I read it wrong. That was really stupid of me. Thanks for your help!