Filament lamps operate normally at a power factor of:
Show Hint
- 0.6 lagging
- 0.6 leading
- Zero power factor
- Unity power factor
The Correct Option is D
Solution and Explanation
Step 1: Understanding Power Factor The power factor of an electrical load is defined as: \[ \text{Power Factor} = \cos \theta = \frac{\text{Real Power}}{\text{Apparent Power}} \]
Step 2: Power Factor of Filament Lamps
- Filament lamps (incandescent lamps) consist of a resistive heating element (usually tungsten).
- In a purely resistive circuit, voltage and current are in phase, leading to a unity power factor (\( \cos \theta = 1 \)).
Step 3: Evaluating options:
- (A) Incorrect: A lagging power factor is associated with inductive loads (motors, transformers).
- (B) Incorrect: A leading power factor is associated with capacitive loads.
- (C) Incorrect: A zero power factor is observed in circuits dominated by pure reactance (inductors or capacitors).
- (D) Correct: Filament lamps have a unity power factor as they behave like a pure resistive load.
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