Page 110 - Basic Electrical Engineering

or, I R = IR + IR + IR + IR 4
1
eq
3
2
or, R = R + R + R + R 4
3
1
eq
2
Assuming Req as equal to R,

R = R + R + R + R . (2.1)
4
1
2
3
Thus, when resistances are connected in series, the total equivalent
resistance appearing across the supply can be taken as equal to the sum of the

individual resistances.

2.3.2 Parallel Circuits

When a number of resistors are connected in such a way that both the ends of
individual resistors are connected together and two terminals are brought out
for connection to other parts of a circuit, then the resistors are called

connected in parallel as shown in Fig. 2.10. Voltage V is connected across
the three resistors R , R , R connected in parallel. The total current drawn
3
1
2
from the battery is I. This current gets divided into I , I , I such that I = I +
1
2
1
3
I + I . As voltage V is appearing across each of these three resistors,
2
3
applying Ohm’s law we write