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Example 9. For the circuit shown below, the switch has been in position a for a long time and it is moved to b at t=0. Determine the initial and final values the inductor voltage and current i L (0 ) , vL (0 ) , i L () , v L () 9 kΩ t=0 1 kΩ a b + _ 10 V 1 kΩ + i L (t ) vL 10 mH _ 20 V + _ An instantaneously change in inductor current is impossible because the infinite voltage diL would be required. This means the inductor current must be continuous. v L L dt 10 i L (0 ) i L (0 ) 1mA 9 1 v L (0 ) 0V t>0 b 1 kΩ 1 kΩ + i L (t ) vL 10 mH _ 20 V + _ v L (0 ) 20 1 (1 1) 18V For a circuit with dc source, if the circuit stays for a very long time without any switching taking place, we say that the circuit is in the steady state. In the steady sate mode, all the diL 0 . So the currents in the circuit are constants and their derivatives are zero. v L L dt inductor behaves as a short circuit. 20 i L () 10 mA 11 v L () 0V