A circular coil enclosing an area of 120 cm2 is made of 210 turns of copper wire

Question

A circular coil enclosing an area of 120 cm2 is made of 210 turns of copper wire. The wire making up the coil has resistance of 3.0 , and the ends of the wire are connected to form a closed circuit. Initially, a 1.2-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 1.2 T and points downward through the coil. If the time required for the field to reverse directions is 0.30 s, what is the average current in the coil during that time?

_________A

Explanation / Answer

The area is A = 120 x 10^-4 m².

The change in magnetic flux is = AB = (120 x 10^-4 m²) x (1.20 T - (- 1.20 T)) = (120 x 10^-4 m²) x (1.20 T + 1.20 T)) = 0.0288 Wb

The average induced emf is || = N / t = (210 turns x 0.0288 Wb) / (0.100 s) = 20.16 V
The average current is I = / R = 20.16 V / 3.00 = 6.72 A

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