Question

Obtain an expression for effective resistance when two resistors are connected in
(a) series
(b) parallel

Answer 1

In series current is constant

$V=V_1+V_2$

$IR=I{R}_1+I{R}_2$

$R=R_1+R_2$

In parallel voltage is constant

$I=I_1+I_2$

$\frac{V}{R}=\frac{V}{R_1}+\frac{V}{R_2}$

$\frac{1}{R}=\frac{1}{R_1}+\frac{1}{R_2}$