Question

Lamps A and B have filaments of carbon and tangsten respectively. At room temperature the resistance of two bulbs is same. Both are connected in parallel to a 22 V supply. Which of the following statements is correct?

(1) Both bulbs have same intensily

(2) Intensity of bulb A is more than that of B

(3) Intensity of bulb A is less than than B

(4) Initially both have same intensity but, after a sufficiently long time, intensity of bulb A is less than that of B

Answer 1

(1) Both bulbs have same intensily

Since both carbon and tengsten have same resistance (say x) and are connected in parallel the potential drop across each of then is 220 V.

Q₁ = heat produced in carbon filament bulb = (220)²/x

Q₂ = heat produced in tungsten filament bulb = (220)²/x

∴ Q₁/Q₂

Hence both bulbs have the same intensity.