Question

The electric bulbs have tungsten filaments of the same length. If one of them gives $60$ watt and other $100$ watts, then

• A. $100$ watt bulb has thicker filament
• B. $60$ watt bulb has thicker filament
• C. Both filaments are of same thickness
• D. It is possible to get different wattage unless the lengths are different

Answer 1

The correct option is A $100$ watt bulb has thicker filament

We know that,$P=\frac{V^2}{R}$ for same mains circuit V is same.

Thus, $R_{60}>R_{100}$

Also, $R=\frac{\rho L}{A}$ where $\rho =$ resistivity, $A=$area and $L=$ length of wire.

​ Thus less resistor implies more thicker element.

So the 100 W bulb has thicker filament.