Question

A battery with an emf of 12.0 V shows a terminal voltage of 11.8 V when operating in a circuit with two lightbulbs rated at 3.0 W (at 12.0 V) which are connected in parallel. Find the equivalent resistance of the two bulbs in parallel.

Answer 1

`R = 24 ohm`

Step-by-step explanation:

As we know that terminal voltage and EMF of cell is given as

`V = EMF - ir`

`ir = 12 - 11.8`

`ir = 0.2 Volts`

resistance of two bulbs is given as

`R = (V^2)/(P)`

`R = (12^2)/(3)`

`R = 48 ohm`

now these two bulbs are connected in parallel

so equivalent resistance is given as

`(1)/(R) = (1)/(R_1) + (1)/(R_2)`

`(1)/(R) = (1)/(48) + (1)/(48)`

so we have

`R = 24 ohm`