A 25 watt and a 100 watt bulb are joined in series and connected to the mains. Which bulb will grow

Question

A 25 watt and a 100 watt bulb are joined in series and connected to the mains. Which bulb will grow brighter?\

Professor PC Thomas Classes · Answer

Let resistance of 25 watt and 100 watt bulbs be $R_{1}$ and $R_{2}$ respectively. The\ $R_{2}<R_{1}$\ $\left(\because \quad R_{1}=\frac{V^{2}}{25}ight.$ and $\left.R_{2}=\frac{V^{2}}{100}ight)$\ where $V$ is the voltage\ Let the current through each bulb be $i$\ $	herefore \quad$ Heat produced in the first bulb\ $H_{1}=\frac{i^{2} R_{1} t}{4.2}$\ Heat produced in the second bulb\ $H_{2}=\frac{i^{2} R_{2} t}{4.2}$\ $	herefore \quad H_{1}>H_{2}$\ Thus the 25 watt bulb will glow brighter.\