‹ Back to the paper
Solve the following.
Two bulbs B₁ and B₂ having ratings (100W, 220V) and (200W, 220V) are connected in series to a 220V…
Two bulbs $B_{1}$ and $B_{2}$ having ratings (100W, 220V) and (200W, 220V) are connected in series to a 220V supply. Perform necessary calculations to find out which bulb glows brighter.
Answer
Answer
Resistance of each bulb from $R = V^2/P$:
$R_1 = 220^2/100 = 484\ \Omega$, $R_2 = 220^2/200 = 242\ \Omega$.
In series: $I = \frac{220}{484+242} = 0.303\text{ A}$ (same through both).
Power dissipated $P = I^2R$: $P_1 = (0.303)^2\times484 = 44.4\text{ W}$, $P_2 = (0.303)^2\times242 = 22.2\text{ W}$.
Since $P_1 > P_2$, bulb $B_1$ (100 W, 220 V) glows brighter.
Final answer: B1 (44.4 W vs 22.2 W)