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

Answer:

$R = 24 ohm$

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

$R = \frac{V^2}{P}$

$R = \frac{12^2}{3}$

$R = 48 ohm$

now these two bulbs are connected in parallel

so equivalent resistance is given as

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

$\frac{1}{R} = \frac{1}{48} + \frac{1}{48}$

so we have

$R = 24 ohm$