Page 847 - Mechanical Engineers' Handbook (Volume 2)

838 Mechatronics

Time response
t = 0
(t)
+
R • C I IR
–
t
Figure 23 An RC circuit (see Eq. 22b).

V I
C No Yes
L Yes No

The instantaneous behavior (t is small) steady-state behavior (t is large) is also inter-
esting. This shows that a capacitor begins like a short circuit and becomes an open circuit.
Also, an inductor begins as an open circuit and becomes a short circuit:
Capacitor Inductor

t 0 Short Open
t Open Short

1.6 Basic Electronics Examples
Consider the basic circuit in Fig. 24. Applying Kirchhoff’s current law to node A reveals
i i 1 (23)
1
2
Now Kirchhoff’s voltage law can be written as
500i 100i 100 200i 0 (24)
2
2
1
and it is possible to substitute for
i (i 1 i ) (25)
1
1
2
Thus
A
i 1 +
100 Ω 100 Ω
i 2 V out
+
50 Ω 100 V
2 A
–

100 Ω 1 A –

Figure 24 Example electrical circuit.