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Q17. A coil of inductance 0.25 H and resistance 100 Ω is connected to a 200 V d.c. supply via a changeover switch. When the switch is operated the coil is disconnected from the supply and connected in parallel with a 75 Ω resistor.

Calculate EACH of the following for the coil in parallel with the resistor.

a) the energy stored in the coil. (4)

b) the induced e.m.f. at the instant of changeover. (2)

c) the time constant. (2)

d) the initial rate of decay of the current. (3)

e) the current after a time equal to one time constant. (2)

f) the time taken for the current to fall to one third of its original value (3)