Question

40. Two lamps ‘A’ rated 100 Watt 220 V and 'B' rated 60 Watt 220 are connected in series to electric main supply of 220V. The ratio of heat produced in lamp 'A' to the lamp 'B' would be: [Delhi NTSE Stage I/2015] (B) 5:3 (C) 4:5 (D) 5:4 (A) 3:5​

Answer 1

Answer:

Given parameters

Potential difference (V) = 220 V

Power of lamp 1 (P1) = 100 W

Power of lamp 2 (P2) = 60 W

Both the bulbs are connected in parallel. Therefore, the potential difference across each of them will be 220 V, because no division of voltage occurs in a parallel circuit.

We know that

Power = Voltage x Current

P = V x I

I = P/V

Lamp 1:

I1 = P1/V

I1 = 100/220

I1 = 5/11 A

Lamp 2:

I2 = P2/V

I2 = 60/220

I2 = 3/11 A

Net current (I) = I1 + I2

I = 5/11 + 3/11

I = 8/11

I = 0.7273 A

Hence, current drawn from the line is 0.727 A

Answer 2

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