Average induced emf in coil with turns

1. Feb 25, 2012

susan14

1. The problem statement, all variables and given/known data
A closely wound rectangular coil of 95.0 turns has dimensions of 29.0 cm by 40.0 cm. The plane of the coil is rotated from a position where it makes an angle of 39.0 degrees with a magnetic field of 1.60 T to a position perpendicular to the field. The rotation takes 0.120 s.
What is the average emf induced in the coil?

2. Relevant equations

3. The attempt at a solution
ε=ΔB/Δt*(A*cos 39°)
ε=1.6/.120*(.116*cos39)
=1.20

2. Feb 26, 2012

I like Serena

Welcome to PF, susan14!

Which formula do you have for the emf?

I have:
$$\mathcal{E}=-N {d\Phi \over dt}$$
where either $\Phi = B_{\textit{perpendicular to A}} A$ or $\Phi = B A_{\textit{perpendicular to B}}$.

The average $\mathcal{E}$ would be:
$$\mathcal{E}_{average}=-N {\Delta\Phi \over \Delta t}=-N {\Phi_t - \Phi_0 \over t - 0}$$
where $\Phi_0$ is the magnetic flux at time t=0, and $\Phi_t$ is the magnetic flux at the final time t.

What would you get for $\Phi_0$ and for $\Phi_t$?
And what did you do with the factor N?