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514 ⏐⏐⏐ INDUCTORS
E
R 1
4.7 k�
36 V
i L
FIG. 12.72
Problem 15.
I 4 mA R 1 = 2.2 k�
20 V
–
vR2 R2 +
vL L
+ –
120 mH
8 mA
i L
FIG. 12.73
Problem 16.
R 2
+ vL –
L = 200 mH
R 1
R 2
8.2 k�
3 mA
E
i L
3.9 k�
10 k�
+
R2 10 k� L 10 mH vL –
FIG. 12.74
Problems 17, 45, and 46.
8.2 k�
E – 6 V
R 1
FIG. 12.75
Problem 18.
i L
6.8 k�
–
L 5 mH vL +
i L
16 V
15. For the network of Fig. 12.72:
a. Write the mathematical expressions for the current i L
and the voltage v L following the closing of the switch.
Note the magnitude and direction of the initial current.
b. Sketch the waveform of i L and v L for the entire period
from initial value to steady-state level.
*16. For the network of Fig. 12.73:
a. Write the mathematical expressions for the current i L
and the voltage v L following the closing of the switch.
Note the magnitude and direction of the initial current.
b. Sketch the waveform of i L and v L for the entire period
from initial value to steady-state level.
SECTION 12.9 R-L Transients: Decay Phase
17. For the network of Fig. 12.74:
a. Determine the mathematical expressions for the current
iL and the voltage vL when the switch is closed.
b. Repeat part (a) if the switch is opened after a period
of five time constants has passed.
c. Sketch the waveforms of parts (a) and (b) on the same
set of axes.
*18. For the network of Fig. 12.75:
a. Write the mathematical expression for the current i L
and the voltage v L following the closing of the switch.
b. Determine the mathematical expressions for i L and v L
if the switch is opened after a period of five time constants
has passed.
c. Sketch the waveforms of i L and v L for the time periods
defined by parts (a) and (b).
d. Sketch the waveform for the voltage across R 2 for the
same period of time encompassed by i L and v L. Take
careful note of the defined polarities and directions of
Fig. 12.75.