• # question_answer The two electric bulbs have 40 watt and 60w rating at 220V. Then the ratio of their resistance will be: A)  1 : 4              B)  3 : 2 C)  4 : 3              D)  2 : 3

Here: ${{P}_{1}}=40W,{{P}_{2}}=60W$ voltage = 220V Using the relation for power $P=\frac{{{V}^{2}}}{R}\propto \frac{1}{R}$ Or $R\propto \frac{1}{P}$ Hence, $\frac{{{R}_{1}}}{{{R}_{2}}}=\frac{{{P}_{2}}}{{{P}_{1}}}=\frac{60}{40}=\frac{3}{2}$ Ratio of${{R}_{1}}$and${{R}_{2}}$is$3:2$