In which one among the following situations, the bulb would glow the most ? (Consider all batteries are the same)
Diagram (a)
Diagram (b)
Diagram (c)
Diagram (d)
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-2 – 2024
– Assuming each battery provides a voltage V:
– Diagram (a) (one battery, one bulb): Voltage across bulb = V.
– Diagram (b) (two batteries in series, one bulb): The voltages of batteries in series add up. Total voltage = 2V. This voltage is across the bulb.
– Diagram (c) (two batteries in parallel, one bulb): Batteries in parallel maintain the same voltage as a single battery (assuming identical ideal batteries). Total voltage = V. This voltage is across the bulb. (Parallel connection increases total current capacity, but not voltage).
– Diagram (d) (one battery, two bulbs in series): The voltage V from the battery is divided between the two bulbs. Assuming identical bulbs, voltage across each bulb = V/2.
– Comparing the voltage across the bulb in each case: (a) V, (b) 2V, (c) V, (d) V/2.
– Since the power dissipated (and thus brightness) is proportional to V², the bulb will glow brightest when the voltage across it is highest, which is in case (b) with two batteries in series (2V).