Question

A bulb is connected to a cell. How is the resistance of circuit affected if another identical bulb is connected in parallel ?

• A. Resistance is tripled.
• B. Resistance remains same.
• C. Resistance is doubled
• D. Resistance is halved

Answer 1

The correct option is D Resistance is halved

A circuit composed solely of components connected in parallel is known as a parallel circuit. In a parallel circuit, the voltage across each of the components is the same, and the total current is the sum of the currents through each component.

To find the equivalent resistance of all components, the reciprocals of the resistances of each component is added and the reciprocal of the sum is taken. That is,

$\frac{1}{R_{equi}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}$.

When a bulb of the same resistance is connected in parallel, the total resistance in the circuit is given by,

$\frac{1}{R_{equi}}=\frac{1}{R}+\frac{1}{R}=\frac{2}{R}$

Hence, $R_{equi}=\frac{R}{2}$

Hence, the resistance is halved.