Question

Several electric bulbs designed to be used on a 220V electric supply line, are rated 10W. How many lamps can be connected in parallel with each other across the two wires 220 V line if the maximum allowable current is 5A?

Answer 1

So here is the answer to your question. It is 110bulbs.
And the method is in the picture.














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Answer 2

Since P = Vi

⇒10 W = 220 V × i

⇒10/220 or 1/22 A = i

Now, R = V/i

⇒R = 220 V/ (1/22) A

⇒R = 4840 Ω

Since such "2" wires are being used so total resistance will be

⇒ 4840 × 2 = 9680 Ω

Similarily, the actual resistance that can be due to actual current of 5 A which can be provided is

⇒ R = 440 V/5 A = 88 Ω

So total bulbs to be needed = 9680/88

⇒110 bulbs