the applied voltage (Figure 27D). At this time, the input pulse

decays to zero and a back emf is developed across the inductor. This

voltage is equal and opposite to ER, or 63 percent of E. The

current and the resistor voltage now decrease towards zero at a rate

determined by the universal time constant chart. After 1 time

constant, the current and ER are both equal to 37 percent of the

values from which they started to decrease, or approximately 23

percent of their steadystate values. At the same time, EL is

decreasing to approximately 23 percent of E. During the next half

cycle, the current and the resistor voltage start increasing from a

value equal to approximately 23 percent of their steadystate values

and, therefore, reach a higher value than they did during the first

halfcycle when they started increasing from zero. During each

succeeding cycle, the current and the resistor voltage reach a

slightly higher value than they did during the previous cycle, until

a point is reached where ER varies equally above and below the

average value of the applied voltage (50 volts in the circuit

illustrated), and the current varies equally above and below an

average value of 50 volts divided by 100 ohms (value of R) or 0.5

amperes. The inductor voltage at this time varies equally above and

below the zero volt axis.

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