30.

Because of the property of inductance to oppose a change in current, a certain amount of time is required

for current change. The time it takes the current in a circuit containing only resistance, inductance, and a d-

c voltage source to change 63.2 percent of its value, is known as the L/R TIME CONSTANT. The time

constant is determined by the ratio of circuit inductance to circuit resistance. The mathematical equation is:

where TC = time constant in seconds

L = circuit inductance in henrys

R = circuit resistance in ohms

Calculate the L/R time constant of a circuit with 2h of inductance and 10 of resistance.

31.

On the inductive waveforms shown below, label the current and voltage waveform.