A 115-turn circular coil of radius 2.71 cm is immersed in a uniform magnetic field that is perpendicular to the plane of the coil. During 0.133 s the magnetic field strength increases from 50.1 mT to 90.5 mT. Find the magnitude of the average EMF, in millivolts, that is induced in the coil during this time interval.

80.6 mV

Explanation:

Parameters given:

Number of turns, N = 115

Radius of coil, r = 2.71 cm = 0.0271m

Time taken, t = 0.133s

Initial magnetic field, Bin = 50.1 mT = 0.0501 T

Final magnetic field, Bfin = 90.5 mT = 0.0905 T

Induces EMF is given as:

EMF = [(Bfin - Bin) * N * A] / t

EMF = [(0.0905 - 0.0501) * 115 * pi * 0.0271²] / 0.133

EMF = (0.0404 * 115 * 3.142 * 0.0007344) / 0.133

EMF = 0.0806 V = 80.6 mV

there are no contact forces mentioned on the list of choices that you've provided.