PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Direct Current and Transient Analysis 113

R.2.54 The equivalent resistance Req of a set of two resistors R 1 and R 2 connected in series,

as illustrated in Figure 2.7, is given by its sum.

If n resistors are connected in series (n > 2) denoted by R 1 , R 2 , R 3 , ..., Rn, then the

equivalent resistance Req is given by

RRi

i

n

eq



 1

∑

R.2.55 The equivalent resistance Req of two resistors R 1 and R 2 connected in parallel is

given by

R

RR

eq RR



12

12

*

and for the case of the three resistors, the equivalent resistance is given by

R

RRR

eq RR RR RR



123

12 23 31

**

***

For the case of n (n > 3) resistors (R 1 , R 2 , R 3 , ..., Rn) connected in parallel, the equiva-

lent resistance is given by

111 1

RRReq 12 Rn



1

Req

1

i 1 Ri

n

∑

or

R

i Ri

eq n

1

1

∑ 1

FIGURE 2.7

Series equivalent resistor.

R 1

R 2

Req = R 1 + R 2

~~