The current passing through an inductor coil of 5H is decreasing at the rate of 2A/s, the emf developed across the coil is :

+ 10.0 V

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- 10.0 V

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+ 2.5 V

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- 2.5 V

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Solution

The correct option is A + 10.0 V
If on changing current through the coil, the emf induced in the coil is e, then by Faraday's $2^{n d}$ law, we have
$e = - L \frac{△ i}{△ t}$
Where, $\frac{△ i}{△ t}$ is rate of change of current.
Given, $L = 5 H \frac{△ i}{△ t} = - 2 A / s$ (decreasing)
$∴ e = - 5 \times (- 2) = + 10 V$

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The current passing through an inductor coil of 5H is decreasing at the rate of 2A/s, the emf developed across the coil is :

The correct option is A + 10.0 VIf on changing current through the coil, the emf induced in the coil is e, then by Faraday's 2nd law, we have e=−L△i△tWhere, △i△t is rate of change of current.Given, L=5H△i△t=−2A/s (decreasing)∴e=−5×(−2)=+10V