Page 26 - Schaum's Outline of Theory and Problems of Electric Circuits

CIRCUIT CONCEPTS
CHAP. 2]

Fig. 2-10 15

Fig. 2-11

2.4 An inductance of 3.0 mH has a voltage that is described as follows: for 0 > t > 2 ms, V ¼ 15:0V
and, for 2 > t > 4 ms, V ¼ 30:0 V. Obtain the corresponding current and sketch v L and i for
the given intervals.
For 0 > t > 2 ms,
ð ð
1 t 1 t 3
i ¼ vdt ¼ 15:0 dt ¼ 5 10 t ðAÞ
L 0 3 10 3 0
For t ¼ 2 ms,
i ¼ 10:0A

For 2 > t > 4 ms,
ð ð
1 t 1 t
i ¼ vdt þ 10:0 þ 30:0 dt
L 2 10 3 3 10 3 2 10 3
1
3
¼ 10:0 þ ½ 30:0t þð60:0 10 ފ ðAÞ
3 10 3
3
¼ 30:0 ð10 10 tÞðAÞ
See Fig. 2-12.

3
2.5 A capacitance of 60.0 mF has a voltage described as follows: 0 > t > 2 ms, v ¼ 25:0 10 t (V).
Sketch i, p, and w for the given interval and find W max .
For 0 > t > 2 ms,