Page 112 - MATLAB an introduction with applications

CHAPTER 2 22

Electrical Circuits

2.1 INTRODUCTION
In this chapter, we briefly review the three types of basic passive electrical elements: resistor, inductor and
capacitor.
Resistance Elements: Ohm’s Law: The voltage drop V R across a linear resistor is proportional to the current
i R flowing through the resistor, where the constant of proportionality is the resistance R as shown in Fig. 2.1.
R
i R
+ –
V R
Fig. 2.1
V R = R i R
Resistors do not store electrical energy in any form but dissipate it as heat. The rate of energy dissipated
(power consumed) by a resistor is given by
V 2
2
i
P = R R = R (W or J/s)
R
Resistors in Series: The current i passes through each element as shown in Fig. 2.2(a). The total voltage
drop is given by the sum of the voltage drops across each element, or
V = V 1 + V 2
Applying Ohm’s law, we obtain
iR eq = iR 1 + iR 2
or R eq = R 1 + R 2
The voltage drop across each resistor is then given by
 R 
V = 1 V
1   R + R  
2
1

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