College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 80

An electromagnet can be modeled as an inductor in series with a resistor. Consider a large electromagnet of inductance L = 12.0 H and resistance R = 4.50 V connected to a 24.0 V battery and switch as in Figure P20.43. After the switch is closed, find (a) the maximum current carried by the electromagnet, (b) the time constant of the circuit, and (c) the time it takes the current to reach 95.0% of its maximum value.