A circuit has a fuse having a rating of 5 A. What is the maximum numbe

A circuit has a fuse having a rating of 5 A. What is the maximum number of 100 W-220 V bulbs that can be safely connected in parallel in the circuit?

[amp_mcq option1=”20″ option2=”15″ option3=”11″ option4=”10″ correct=”option4″]

This question was previously asked in

UPSC CDS-2 – 2018

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A maximum of 11 bulbs can be safely connected in parallel in the circuit.

The circuit has a fuse rating of 5 A, which means the total current drawn by all connected devices must not exceed 5 A to prevent the fuse from blowing. Each bulb is rated at 100 W at 220 V. The current drawn by a single bulb is calculated using the formula P = V * I, so I = P/V.
Current per bulb = 100 W / 220 V = 10/22 A = 5/11 A.
When bulbs are connected in parallel, the voltage across each bulb is the same (220 V), and the total current drawn from the source is the sum of the currents drawn by each bulb. Let N be the number of bulbs connected. The total current is N * (5/11) A.
For safe operation, the total current must be less than or equal to the fuse rating: N * (5/11) A ≤ 5 A.
N * 5 ≤ 5 * 11
N ≤ 11.
Since the number of bulbs must be a whole number, the maximum number of bulbs that can be safely connected in parallel is 11.

Fuses are safety devices designed to protect electrical circuits from excessive current that could cause overheating and potentially fire. They are intentionally the weakest point in the circuit and melt, breaking the connection, if the current exceeds their rated value. Parallel connections are common for household appliances like lights, allowing each device to operate independently at the full circuit voltage.

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