Question

A coil of self inductance 50 henry is joined to the terminals of a battery of e.m.f. 2 volts through a resistance of 10 ohm and a steady current is flowing through the circuit. If the battery is now disconnected, the time in which the current will decay to 1/e of its steady value is

• A. 500 seconds
• B. 50 seconds
• C. 5 seconds
• D. 0.5 seconds

Answer 1

Answer: (C)

5 seconds

Answer 2

Time in which the current will decay to $\frac { 1 } { e }$of its steady value is $t = \tau = \frac { L } { R } = \frac { 50 } { 10 } = 5$seconds