1. Aug 21, 2011

### Moh'd Ali MQN

A 25-turn circular coil of wire has diameter 1.00 m. It is placed with its axis along the direction of the Earth’s magnetic field of 50.0 /T, and then in 0.200 s it is flipped 180°. An average emf of what magnitude is generated in the coil?

This is a question in my book and the answer was
http://store1.up-00.com/Jun11/M8h57751.p… [Broken]
Why didnt we use the formula where we derive the angle as : E=-N.d(BAcos(wt))/dt
My solution was as follows:
E = -NBAw.sin(wt), where w = 2.pi/t
E = -NBAw.sin(180) = 0 and this was logical to me because the final emf in the coil is zero and we get an average of zero. Unless there is another meaning of average emf......