The average emf induced into the coil is given by:

$\overline{){\mathbf{\epsilon}}{\mathbf{=}}{\mathbf{N}}\frac{\mathbf{\u2206}\mathbf{\varphi}}{\mathbf{\u2206}\mathbf{t}}}$, where Φ is the magnetic flux, N is the number of turns, and t is the time.

Magnetic flux:

$\overline{){{\mathbf{\varphi}}}_{{\mathbf{B}}}{\mathbf{=}}{\mathbf{B}}{\mathbf{A}}{\mathbf{c}}{\mathbf{o}}{\mathbf{s}}{\mathbf{\theta}}}$, where B is the magnetic field, A is the cross-sectional area of the coil, and θ is the angle between the plane of the coil and the magnetic field.

(Figure 1) shows a 100-turn coil of wire of radius 11cm in a 0.35T magnetic field.

The coil is rotated 90° in 0.30 s, ending up parallel to the field. What is the average emf induced in the coil as it rotates?

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