# Induced Emf in a Rectangular Coil

1. Mar 15, 2012

### SgtMousse

1. The problem statement, all variables and given/known data
A rectangular coil of 90 turns has dimensions of 22 x 65 cm and is located in a uniform 1 T magnetic field. In 1.7 s, the plane of the coil is rotated from a position where it makes an angle of 19° with the magnetic field to a position where it makes an angle of 64°. Calculate the average emf induced in the coil.

2. Relevant equations

emf= -N*(d$\Phi$/dt)
$\Phi$=BAcos$\vartheta$

3. The attempt at a solution

So I calculated the change in flux to be: (B*A*cos(90-64))-(B*A*cos(90-19)=B*A*(cos(26)-cos(71))

I then calculated emf.
emf= - ((90 turns)*(1 T)*(0.22m*0.65m)*(cos(26)-cos(71)))/1.7 s = -4.34 V
This is wrong. I then entered the absolute value, which is also incorrect.

2. Mar 16, 2012

### tiny-tim

Hi SgtMousse!
looks ok

have you tried 4.3 V, since it should be two significant figures ?​

3. Mar 16, 2012

### SgtMousse

Apparently my answer was correct, even though it was marked wrong. I just checked my online homework site, and they marked it correct. They must have had it wrong before. Thanks anyway!