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*19. For the network of Fig. 12.76:
a. Determine the mathematical expressions for the current
i L and the voltage v L following the closing of the
switch.
b. Repeat part (a) if the switch is opened at t � 1 ms.
c. Sketch the waveforms of parts (a) and (b) on the same
set of axes.
SECTION 12.10 Instantaneous Values
20. Referring to the solution to Example 12.4, determine the
time when the current iL reaches a level of 10 mA. Then determine
the time when the voltage drops to a level of 10 V.
21. Referring to the solution to Example 12.5, determine the
time when the current iL drops to 2 mA.
SECTION 12.11 Thévenin Equivalent: t � L/R Th
22. a. Determine the mathematical expressions for i L and v L
following the closing of the switch in Fig. 12.77.
b. Determine i L and v L at t � 100 ns.
*23. a. Determine the mathematical expressions for i L and v L
following the closing of the switch in Fig. 12.78.
b. Calculate i L and v L at t � 10 ms.
c. Write the mathematical expressions for the current i L
and the voltage v L if the switch is opened at t � 10 ms.
d. Sketch the waveforms of i L and v L for parts (a) and (c).
E
12 V
I =
4 mA R 1
R 1
FIG. 12.76
Problem 19.
PROBLEMS ⏐⏐⏐ 515
2 k�
+
R2 10 k� L 1 mH vL –
R 2
24 k�
iL +
12 k� L 2 mH vL –
FIG. 12.77
Problem 22.
E = + 8 V
R 1
2.2 k�
R2 4.7 k� L 10 mH vL –
FIG. 12.78
Problem 23.
i L
+
i L