PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

190 Practical MATLAB® Applications for Engineers

Note that the symbolic results shown in Figure 2.90 fully agree with the numerical

results shown in Figure 2.91.

Example 2.27

Steady-state conditions exist in the network shown in Figure 2.92 at t = 0 −, when the

V 1 = 10 V source is connected to the RC circuit. At t = 0 +, the switch moves downward,

and the V 2 = 20 V source is connected to the RC circuit (while the source V 1 = 10 V is

disconnected), for t ≥ 0.

1. Write and solve the loop differential equation by hand, for the current i(t) (through
   RC) and the voltages vR(t) and vC(t), for t ≥ 0.


2. Create the script fi le RC_ IC that returns the solutions for part 1 using the MATLAB
   symbolic solver dsolve.


3. Repeat part 1 by using the MATLAB numerical solver ode45.


4. Also, obtain the plots of
   a. i(t) versus t
   b. vR(t) versus t
   c. vc(t) versus t
   over the range 0 ≤ t ≤ 2 s, for parts 2 and 3.

FIGURE 2.91

Plots of numerical transient solutions of Example 2.26.

1.61.41.210.80.60.40.20 21.8

6

4

8

10

plots of [i(t), vr(t), and vL(t)] versus t

i(t) in amps

vr(t) in volts

vL(t) in volts

1.61.41.210.80.60.40.20 21.8

10

15

10

1.61.41.210.8 21.8

time in sec

0.60.40.20

0

5

10