Question

In an electrical circuit three incandescent bulbs A, B and C of rating 40 W, 60 W and 100 W respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?

Options

• Brightness of all the bulbs will be the same

• Brightness of bulb A will be the maximum

• Brightness of bulb B will be more than that of A

• Brightness of bulb C will be less than that of B

Answer 1

Brightness of bulb B will be more than that of A

Explanation - 

Since all the three bulbs are connected in parallel so potential difference (V) across all the bulbs is same. Power dissipated is given by 

`"P" = "V"^2/"R"`

Lower the resistance, higher the power dissipation. Hence higher the brightness.

Out of all the three bulbs, 100 W bulb will have minimum resistance because rated voltage of all the bulbs will be same and its power dissipation is maximum.

Thus, 100 W will have maximum brightness and 40 W bulb will have minimum brightness.