Draw the parallel combination circuit diagram and establish the essential formula to calculate equivalent resistance.

First, we will look at the circuit diagram of the resistors in parallel combination and as we know that resistors in parallel have the same amount of potential difference across them but the amount of current passing through each resistor is different.

The total current I, is equal to the sum of the

separate currents through each branch of the combination.

I = I₁ + I₂ + I₃

Let Rp be the equivalent resistance of the parallel combination of

resistors. By applying Ohm’s law to the parallel combination of resistors, we have

On applying Ohm’s law to each resistor, we have

we have

or

Thus, we may conclude that the reciprocal of the equivalent resistance of a group of resistances joined in parallel is equal to the sum of the reciprocals of the individual resistances.