A heater of resistance 5 ohm is connected to a 10 V supply. What power does it dissipate?

Answer and explanation

Correct answer: D. 20 W

  1. Step 1: Power P = V^2 / R.
  2. Step 2: P = 10^2 / 5 = 20 W.
Answer
20 W.
Why not the others: '2 W' gives the current in amperes, not the power; '50 W' multiplies V and R; '10 W' includes an unnecessary factor 1/2.

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