Question

Two bulbs are rated (P₁, V) and (P₂, V). If they are connected (i) in series and (ii) in parallel across a supply V, find the power dissipated in the two combinations in terms of P₁ and P₂.

Answer 1

Resistances of the two bulbs R₁ = \(\frac{V^2}{P_1}\) and R₂ = \(\frac{V^2}{P_2}\)

(i) Net resistance in series

R_s = R₁ + R₂ = \(\frac{V^2}{P_1} + \frac{V^2}{P_2} = V^2 (\frac{P_1+P_2}{P_1P_2})\)

(ii) Net resistance in parallel