a) A circular loop in the plane of the paper lies in a 0.55 T magnetic field poi

Question

a) A circular loop in the plane of the paper lies in a 0.55 T magnetic field pointing into the paper. The resistance of the coil is 2.40 . If the loop's diameter changes from 22.5 cm to 6.50 cm in 0.40 s, what is the average induced current in milli-amps?

b)  A magnetic field is perpendicular to the plane of a single-turn circular coil. The magnitude of the field is changing, so that an emf of 0.63 V and a current of 2.9 A are induced in the coil. The wire is the re-formed into a single-turn square coil, which is used in the same magnetic field (again perpendicular to the plane of the coil and with a magnitude changing at the same rate). What current is induced in the square coil?

Explanation / Answer

a) Induced emf = d(BA)/dt = B*dA/dt (this is because B is constant)

= 0.55*(A2-A1)/t = 0.55*pi*(0.225^2-6.50^2)/0.40=182.28V

So current = induced emf/resistance = 182.28/0.40=455.7A

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