Vidyalelo
Physics GK · Q310

Electricity and Magnetism

Competitive Exams · Physics GK · question 310

Q310

Of the two bulbs,one glows brighter than the other. Which bulb has a higher resistance?

A.
Brightness is independent of resistance
B.
The bright bulb
C.
Both have the same resistances
Answer
D.
The dim bulb

Answer: Option C

Solution

Answer: Option C
Solution:
The brightness of a bulb depends on the power (P) it dissipates, which is given by the relation:

P = V² / R (when the bulbs are connected in parallel)

or

P = I² × R (when the bulbs are connected in series)

When two bulbs are connected to the same voltage supply, the bulb with the lower resistance allows more current to flow through it and therefore dissipates more power, making it brighter.

On the other hand, the bulb with the higher resistance allows less current to pass through, so it dissipates less power and glows dimly.

Thus, the dim bulb always has the higher resistance when both bulbs are connected across the same voltage source.

Therefore, the correct answer is Option D: The dim bulb.