A circular coil enclosing an area of 160 cm2 is made of 210 turns of copper wire

Question

A circular coil enclosing an area of 160 cm2 is made of 210 turns of copper wire. The wire making up the coil has resistance of 7.0 , and the ends of the wire are connected to form a closed circuit. Initially, a 2.0-T uniform magnetic field points perpendicularly upward through the plane of the coil. The direction of the field then reverses so that the final magnetic field has a magnitude of 2.0 T and points downward through the coil. If the time required for the field to reverse directions is 0.20 s, what is the average current in the coil during that time?

Explanation / Answer

Change in magnetic flux is = AB = (160 x 10^-4 m²) x (2 T - (- 2 T)) = (160 x 10^-4 m²) x (2 T + 2 T)) = 0.064 Wb

Average induced emf is || = N / t = (210 turns x 0.064 Wb) / (0.2 s) = 67.2 V

The average current is I = / R = 67.2 V / 7 = 9.6 A

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