Question

derive the expression for net resistance of three resistance R1 , R2 , R3 are connected in parallel combination​

Answer 1

Total Current I, is equal to the sum of the separate currents through each branch

I:I1 +I2 +I3 .........1

Let RP be the equivalent resistance of parallel resistors.

By Ohms law,

I:V/RP

Applying Ohms law to each resistor,we have

I1:V/R1 ......2

I2:V/R2 ........3

I3:V/R3 .......4

From 1,2,3 and 4

we get ,

V/Rp:V/R1+V/R2+V/R3

or

1/Rp:1/R1+1/R2+1/R3

{wherever there is : please mark it as "equal to"}