Two conducting wires of the same material and of equal lengths and equal diameters are first connected in parallel and then in series in a circuit across the same potential difference. The ratio of heat produced in parallel and series combinations is

  1. A. 2:1
  2. B. 4:1 ✓
  3. C. 1:2
  4. D. 1:4

Correct Answer: B. 4:1

Explanation

Let the resistance of each wire be R. In parallel, equivalent resistance R_{p} = R/2. In series, R_{s} = 2R. Heat produced H = V^2/R * t. Therefore, H_{p}/H_{s} = R_{s}/R_{p} = (2R) / (R/2) = 4/1, giving a ratio of 4:1.

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