Question

Deriv ethe equivalent resistance in series and parallel combination

Answer 1

FOR SERIES:-

Let drop on R1 be V1 & drop on R2 be V2.  

Total voltage V=V1+V2  

We know that V=I*R(ohms law)  

So I*R=(I*R1)+(I*R2)  

R=R1+R2

FOR PARALLEL:-

Let current through R1 be I1 & current through R2 be I2.  

I=V/R(ohms law)  

So I=I1+I2  

V/R=(V/R1)+(V/R2)  

1/R=(1/R1)+(1/R2)  

R=(R1*R2)/(R1+R2)

Hence they are derived.

Answer 2

Answer:

$\huge\mathtt \red {\xcancel{ \longmapsto\frac{V\left(R_{2}+R_{3}\right)}{R_{1}R_{2}+R_{1}R_{3}+R_{2}R_{3}}}}$