Question

Two electric bulbs of 50 watt and 100 watt are given. Which one will be brighter when they are connected (a) in series, and (b) in parallel?

Answer 1

In series circuit the bulb with lower value of power rating will glow brighter and in parallel circuit bulb with higher value of power rating will glow brighter.

Thus is because current remains same in series circuit while voltage is constant in a parallel circuit. A higher wattage bulb will have more resistance as well.
Therefore, 40 W will glow brighter in series circuit and 100 W will glow brighter in parallel circuit.