The switch S1 is close at time t=0 and the switch S2 is kept open. At some later time ( t0 ), the switch S1 is opened and S2 is closed. The behaviour of the current I as a function of time ' t ' is given by:
(A)(see structure)
(B)(see structure)✓ Correct
(C)(see structure)
(D)(see structure)
Answer: (B)
Solution
When S1 closes the inductor resists the sudden appearance of current, so the current climbs from zero and approaches its steady value along the familiar exponential LR growth curve. At the instant t0, when S1 is opened and S2 closed, the inductor now insists on continuity of current and drives it around the new loop, so the current falls exponentially back towards zero. The behaviour is therefore a rising exponential up to t0 followed by a falling exponential afterwards.
JEE Main · 2019 · 11 Jan 2019 · Shift 1 · Single correct option
