PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Direct Current and Transient Analysis 189

figure(2)

subplot(3,1,1)

plot(t,it)

title(‘plots of [i(t), vr(t), and vL(t)] vs t’)

ylabel(‘i(t) in amps’)

subplot(3,1,2)

vr=R*it’;

plot(t,vr);ylabel(‘vr(t) in volts’);

subplot(3,1,3)

vl=20*ones(1,45)-vr;plot(t,vl);

ylabel(‘vL(t) in volts ‘);xlabel(‘time in sec’)

function didt=f(t,i)

didt=20-2*i;

The script fi le RC_ IC is executed, and the results and plots are shown in Figures 2.90

and 2.91.

>> RC _ IC

***************************************

**********R E S U L T S **************

***************************************

The i(t) for t >0 is:

it _ 1 =

10-5*exp(-2*t)

The voltage across R=2 ohms is :

vtr _ 1 =

20-10*exp(-2*t)

The voltage across L=1 henry is :

vl _ 1 =

10*exp(-2*t)

********Verify solution************

verify = diff(it _ 1,t)+2*it _ 1

verify =

20

*************************************

FIGURE 2.90

Plots of symbolic transient solutions of Example 2.26.

1.41.21 21.81.6

t

t

0.60.40.20 0.8

6

8

10

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

i(t) in amps

vr(t)

vL(t)

0.60.40.20 1.41.210.8 21.81.6

10

15

20

1.41.21 21.81.6

time in sec

0.60.40.20 0.8

0

5

10