3 DC circuit analysis
3.1 INTRODUCTION
Circuit analysis is important in order to be able to design, synthesize and
evaluate the performance of electric circuits or networks. The two basic laws
for circuit analysis are Kirchhoff's current law (KCL), sometimes referred to as
the first law and Kirchhoff's voltage law (KVL), sometimes called the second
law. However, a number of techniques have been developed, in the form of
network theorems, for simplifying the analysis in the case of more complicated
circuits. These theorems, which are introduced in this chapter, are applicable to
linear circuits, both a.c. and d.c., but it is convenient to consider d.c. circuits
only to begin with because they are a little simpler mathematically and the
concepts are that much easier to grasp.
When you have studied this chapter you should be able to calculate the
current, voltage and power in any element of most commonly encountered d.c.
circuits.3.2 DEFINITION OF TERMS
It will be useful first of all to define terms, and Fig. 3.1 will be used for this
purpose. It shows a five-element circuit of which one (the battery or voltage
source) is active and the other four (resistors) are passive.1 t R1 I12 R_2 J I2 3V R34
5
Figure 3.1
9 Node: a point at which two or more elements have a common connection is
called a node. Thus there are six nodes in the circuit, numbered 1-6.