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A 12 V battery connected to a coil of resistance 6 Ω through a switch, drives a constant current in the circuit. The switch is opened in 1 ms. The emf induced across the coil is 20 V. The inductance of the coil is :

1. 10 mH
2. 8 mH
3. 5 mH
4. 12 mH

Correct answer: 10 mH

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