schaum's outlines of signals and systems

Page 168

LAPLACE TRANSFORM AND CONTINUOUS-TIME LTI SYSTEMS

CHAP. 31

(b)

Fig. 3-16

From Fig. 3-16(b) the loop equation can be written as

or Hence,

Taking the inverse Laplace transform of I(s), we obtain

Note that i(O+) = 2 = i(0-); that is, there is no discontinuity in the inductor current before and after the switch is opened. Thus, we have

3.42. Consider the circuit shown in Fig. 3-17(a). The two switches are closed simultaneously at t = 0. The voltages on capacitors C, and C, before the switches are closed are 1 and 2 V, respectively.

(a) Find the currents i , ( t ) and i,(t). ( b ) Find the voltages across the capacitors at (a)

t = 0'

From the given initial conditions, we have uCl(O-) = 1 V

and

L!=~(O-)= 2 V

Thus, using Fig. 3-10, we construct a transform circuit as shown in Fig. 3-17(b). From


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