JEE MAIN - Physics (2022 - 26th June Morning Shift - No. 22)
A 10 $$\Omega$$, 20 mH coil carrying constant current is connected to a battery of 20 V through a switch. Now after switch is opened current becomes zero in 100 $$\mu$$s. The average e.m.f. induced in the coil is ____________ V.
Answer
400
Explanation
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Initially current, $${I_0} = {{20} \over {10}} = 2A$$ (when initially switch closed)
average emf induced in coil $$ = {{Ldi} \over {dt}}$$
$$ \Rightarrow {e_{avg}} = {{20 \times {{10}^{ - 3}} \times (2 - 0)} \over {100 \times {{10}^{ - 6}}}}$$
$${e_{avg}} = 400\,V$$
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