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A coil with n turns and resistance R Ω is joined to a galvanometer whose resistance is 4R Ω. If this arrangement is shifted in t seconds from a region where the magnetic flux is W1 weber to another where it is W2 weber, the current induced in the circuit is

1. (W1 - W2) / (5 R n t)
2. n(W2 - W1) / (5 R t)
3. (W2 - W1) / (5 R n t)
4. n(W2 - W1) / (R t)

Correct answer: n(W2 - W1) / (5 R t)

Solution

Induced emf = n*(W2 - W1)/t and total resistance = R + 4R = 5R, so induced current i = n*(W2 - W1)/(5*R*t).

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