Page 134 - MATLAB an introduction with applications

Electrical Circuits ——— 119

v
i = s
n R n
where i n and R n are the current through resistors n and its resistance, respectively, and v s is the source
voltage. The equivalent resistance, R eq , is given by
1 = 1 + 1 + .... + 1
R eq R 1 R 2 R n
, and the power P , dissipated in each resistor is given by: P = v i .
The source current is given by: i s = v s /R eq n n s n

Ω Ω Ω Ω Ω Ω
V s =48V
18 35 25 47 61 12
Fig. P2.2

P2.3: Figure P2.3 shows an electrical circuit with a voltage source, v s with an internal resistance, r s and a
load resistance, R L . The power P dissipated in the load is given by
2
vR v s r s Battery
P = s L
(R + r s ) 2
L
Write a MATLAB program to plot the power P as a function of R L for 1 ≤ R L ≤ 12 Ω R L
given that v s = 12 V, and r s = 3 Ω.
Fig. P2.3
P2.4: Figure P2.4(a) shows a resistor of R = 5 Ω and an inductor L = 1.4 H connected
in a circuit to a voltage source (RL circuit). When the voltage source applies a rectangular voltage pulse
with an amplitude of V = 12V and a duration of 0.5s as shown in Fig.P2.4(b), the current i(t) in the circuit
as a function of time is given by

V
−
() =
−
it (1 e ( Rt )/ L ) for 0 ≤ t ≤ 0.5s
R
() =
R
it e − (Rt )/ L V (e (0.5 )/ L /1) for 0.5 ≤ t
R
Write a MATLAB program to plot the current as a function of time for 0 ≤ t ≤ 3s.
i(t)
V(V)
R 12
V(t) L

0 0.5 t(s)
(a) (b)
Fig. P2.4

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