Electromagnetism: Determining Induced EMF

[Pi314227]

Homework Statement

There are 3 parts to the question:
A) Determine the induced EMF as a function of time in a circular loop lying perpendicularly to a constant magnetic field if the radius of the loop decreases by r(t) = 5(1-t).
B) Find out the values of the EMF at t= 0,0.1,0.2,...,0.8 seconds.
C) What will be the direction of the current in the loop at t=0 seconds? At what time will the direction of current get reversed?

Relevant Equations

1) Closed loop integral of EMF = -1 times the derivative with respect to time of the integral of B.n
2) Change in EMF = -1 times the derivative of B with respect to time

 

[Delta2]

Your work for a) and b) looks correct to me.

 

[Pi314227]

Your work for a) and b) looks correct to me.

What about part c? Could you help in that?

 

[Delta2]

For c) i think i have to know the direction of the magnetic field B. Also i am not sure what happens at t=1 since the radius becomes zero then, but yes it looks like the EMF changes sign(polarity) at that point and hence the direction of current is reversed.

 

[Pi314227]

For c) i think i have to know the direction of the magnetic field B. Also i am not sure what happens at t=1 since the radius becomes zero then, but yes it looks like the EMF changes sign(polarity) at that point and hence the direction of current is reversed.

Right. The direction of the magnetic field B was not given. Thankyou so much for your help. Appreciate it alot! :)