A 100 W incandescent light bulb operates on a 200 V circuit. What is the electrical resistance of the bulb filament?

Answer and explanation

Correct answer: B. 400 ohms

  1. Step 1: Use the electric power formula relating power, voltage, and resistance: P = V^2 / R.
  2. Step 2: Rearrange for resistance: R = V^2 / P.
  3. Step 3: Substitute values: V^2 = (200)^2 = 40,000.
  4. Step 4: Compute resistance: R = 40,000 / 100 = 400 ohms.
Answer
400 ohms.
Why not the others: '200 ohms' divides V by 1; '2 ohms' divides V by P; '50 ohms' divides P by 2.

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