Question

What is the power factor of an AC circuit containing only a pure resistor?

• A. \(0\)
• B. \(0.5\)
• C. \(1\)
• D. \(-1\)

Hint:

Power factor values for basic AC circuits:
• Pure resistor → \(1\)
• Pure inductor → \(0\) (lagging)
• Pure capacitor → \(0\) (leading) A unity power factor represents maximum efficiency of power usage.

Answer 1

The Correct Option is C

Topic: Alternating Current - Power Factor
Step 1: Understanding the Question:
The power factor indicates how much of the power is being converted into useful work.
It depends on the phase difference between voltage and current.
Step 2: Key Formula or Approach:
Power Factor is given by:
\[ \text{P.F.} = \cos \phi \]
where \(\phi\) is the phase angle.
Step 3: Detailed Explanation:
1. In a purely resistive circuit, the voltage and current are always in phase.
2. This means the phase angle \(\phi = 0^\circ\).
3. Calculate the power factor:
\[ \text{P.F.} = \cos(0^\circ) = 1 \]
4. A power factor of \(1\) implies that the circuit is purely "active" and there is no reactive power.
Step 4: Final Answer:
The power factor is \(1\).