Physics

Problem

A coil of

N

turns and area

A

starts from rest and rotates about a fixed axis in a uniform magnetic field

B

with a constant angular acceleration

\alpha

. The plane of the coil is perpendicular to the field at

t=0

. Which expression gives the instantaneous emf at time

t

? a)

\varepsilon = N B A\, \alpha t\, \cos\!\left(\tfrac{1}{2}\alpha t^{2}\right)

\varepsilon = N B A\, \alpha t\, \sin\!\left(\tfrac{1}{2}\alpha t^{2}\right)

\varepsilon = N B A\, \alpha t\, \sin\!\left(\alpha t^{2}\right)

\varepsilon = \tfrac{1}{2} N B A\, \alpha t\, \sin\!\left(\tfrac{1}{2}\alpha t^{2}\right)