Two bulbs of 70 W and 50 W are connected in parallel to an external potential difference. Which bulb will glow brighter? Why?

Remember in these type of questions we will have to calculate the amount of power dissipated by the bulbs , the bulbs dissipating more power will glow more brightly.

Again we will first evaluate the resistance of each bulb and after that the current flowing in the circuit , then we will put both the values of current and resistance to evaluate the power dissipation by each bulb.

Let the rating voltage of both the bulbs be same as the input voltage which is V volts.

P₁ = , R₁ = , P₁ = 50 W

P₂ = , R₂ = , P₂ = 70 W

Now to calculate the current flowing in the circuit,

The net resistance is R,

R =

Now let’s calculate power dissipation which is ,

P₁ =

P₂ =

Hence power dissipated by the bulb 2 which has 70 W power will glow more brighter than the 50 W bulb 1.

Hence, we got the same answers when the bulbs are connected in parallel combination.