A circular coil enclosing an area of 140 cm 2 is made of 190 turns of copper wir

Question

A circular coil enclosing an area of 140 cm2 is made of 190 turns of copper wire. The wire making up the coil has resistance of 9.0 , and the ends of the wire are connected to form a closed circuit. Initially, a 1.4-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 1.4 T and points downward through the coil. If the time required for the field to reverse directions is 0.40 s, what is the average current in the coil during that time?
_________A

Explanation / Answer

The area is A = 140 x 10^-4 m².
The change in magnetic flux is = AB = (140 x 10^-4 m²) x (1.4 T - (- 1.4 T)) = (140 x 10^-4 m²) x (1.4 T + 1.4 T)) = 0.0392 Wb
The average induced emf is || = N / t = (190 turns x 0.0392 Wb) / (0.40 s) = 18.62 V
The average current is I = / R = 18.62 V / 9 = 2.07 A

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