Question

Two electric bulbs of 40 W and 60 W are given. Which one of the bulbs will glow brighter if they are connected to the mains in (i) series and (ii) parallel?

Answer 1

Dear Student,

◆ Answer -

(i) 40 W bulb glows brighter in series.

(ii) 60 W bulb glows brighter in parallel.

◆ Explanation -

# Prerequisites -

• Brightness of electric bulb is directly proportional to power consumed by it.
• For same voltage rating, resistance is inversely proportional to power rating.
• Hence, 40 W bulb has higher resistance and 60 W bulb will have low resistance.

(i) In series connection -

In series connection, current flowing through bulbs will be constant but voltage will be variable.

Thus, power consumption by bulbs is given by -

P = I²R

As bulb with higher resistance will consume more power, 40 W bulb will glow brighter in series.

(ii) In parallel connection -

In parallel connection, voltage across bulbs will be constant but current will be variable.

Thus, power consumption by bulbs is given by -

P = V²/R

As bulb with lower resistance will consume more power, 60 W bulb will glow brighter in parallel.

Thanks dear...