applied voltage appears across the resistor, the steady state has

been reached and ER is equal to E. The current is then at its

maximum value and is equal to E/R. Since the resistance of the

inductor is negligible, EL is equal to zero when the steady state is

reached.

Figure 17. RL circuit response to a step voltage

b. The voltage, current, and rate of current change during the

transient periods should be more closely examined to see how these

characteristics change with time. From the instantaneous current

Curve A in Figure 18, which is an enlargement of the first portion of

Figure 17C, it can be seen that the current starts from zero and

increases rapidly at first and then tapers off to practically a zero

rate of increase at the end of five time constants. (RL time

constants are discussed in Section II.) Since the

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