Exam Question

Q6 A coil of inductance 2H and unknown resistance is connected to a D.C. supply of 100 volts. After 4ms the current has risen to 75% of its final steady state value. Calculate EACH of the following: (a) the resistance by the coil (6) (b) the energy stored in the coil when the current has reached its steady state value (6) (c) the time taken for the current to fail to 50% of its steady state value when the supply is switched off (4)