Question

Three bulbs of ratings 40W,60W and 100W are designed to work on 220V mains.Which bulb will glow most bright if they are connected in series across the 220V mains?

Answer 1

Resistance of bulb is inversely proportional to its rated power, at same voltage because

P=(V*V)/R

Therefore R (40W bulb) > R (60W bulb) > R (100W bulb).

Hence the bulb across which power dissipation is more will glow brighter.

So in a series of connection, current flowing across each element in the circuit.

So when 40W, 60W and 100W are designed to work on 220V mains in a series, the power dissipation across each of them will be determined according to the luminous capacity of the bulb.

So 40W bulb will blow brighter in this series of connection.