Exam-style question
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Which of the following best describes the power‑dissipation behaviour of a filament lamp as the applied voltage increases?.
- A.Power increases linearly with voltage.
- B.Power increases quadratically with voltage.
- C.Power remains constant regardless of voltage.
- D.Power decreases as voltage increases.
Model answer
What a good answer should say
- Power increases quadratically with voltage.
Explanation
Why this works
Electrical power is P = V × I. For a filament lamp, I ≈ V / R(V) where R(V) rises with V.
At low voltages the resistance is low, so power grows roughly as V². As the lamp heats, R increases, moderating the increase but the overall trend is still a quadratic rise in power with applied voltage, characteristic of a non‑ohmic device.
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