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How many 100 W, 200 V lamps can at most be run in a circuit protected by a fuse rated for a safe current of 5 A?

1. 10
2. 5
3. 20
4. 40

Correct answer: 10

Solution

Each lamp draws 100/200 = 0.5 A; the fuse allows 5 A, so 5/0.5 = 10 lamps.

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