Answer to Question 5

An inductor of inductance 0.14 H is connected to a 12 V supply of negligible internal resistance. The exponential rise of the measured voltage is studied and at a certain time, it is found that the measured voltage is 2.5 V. Calculate the rate of change of the current at this time. 
EMF = 12 V  2.5 V = 9.5 V dI/dt = E/L = 9.5 V ÷ 0.14 H = 68 A s^{1} 