A circular wire loop of radius a and resistance R initially bas a magnetic flux through it due to an external magnetic field. The external field then decreases to zero. A current is induced in the loop while the external field is changing; however this current does not stop at the instant that the external field stops changing. The reason is that the current itself generates a magnetic field, which gives rise to a flux through the loop. If the current changes, the flux through the loop changes as well and an induced emf appears in the loop to oppose the change(a) The magnetic field at the center of the loop of radius a produced by a current i in the loop is given by B = ?oi/2a. IF we use the crude approximation that the field has this same value at all points within the loop. What is the flux of this field through the loop?(e) In solving the examples in this chapter, we ignored the effects described in this problem. Explain why this is a goodapproximation.

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