Induced Current Direction in a Changing Magnetic Field

[JSapit]

Homework Statement

The component of the external magnetic field along the central axis of a 50 turn coil of radius 5.7 cm decreases from 1.8 T to 0 T in 3.3 s.

(a) If the resistance of the coil is 2.8 ohm, what is the magnitude of the induced current in the coil?

(b) What is the direction of the current if the axial component of the field points towards the viewer?

1. CCW
2. CW

Homework Equations

EMF=-(phi)/(time)

Phi=BASin(theta)

The Attempt at a Solution

I found the current using -N(B/t)*A

I found it to be 0.9442 A.

Now I'm just not sure on part B.

 

[Delphi51]

Well, there won't be any current unless the B is changing!
"A changing B causes an E to circulate around it."

Check out Faraday's Law in your textbook or Wikipedia.

 

[JSapit]

B is changing, though. It said in the problem that "B decreases from 1.8T to 0T."

 

[Delphi51]

Yes, B is changing so you will get an emf in the coil, causing a current.
I meant that any formula you find for the emf MUST have a changing B.
Faraday's Law is what you are looking for.