Class 4 (4th Engineer) MET 📅 Sep 2024

Exam Question

(a) Explain power factor with a.c. Sine wave and phasor diagram. (6)

(b) A circuit has a resistance value of 25 Ω and an inductunce value of 0.3 H. If it is connected to a 230V. 50Hz supply, find the circuit current, the power factor and the power dissipation. (10)

Reference Answer

### (a) Explanation of Power Factor with Sine Wave and Phasor Diagram (6 Marks)
#### 1. Definition and Concept
Power Factor (PF) is a dimensionless measure of the efficiency of an AC electrical system. It is defined as the ratio of the **True Power (P)**, which performs useful work, to the **Apparent Power (S)**, which is the total power supplied by the source.
* **True Power (P)**: Also known as Real or Active Power, measured in Watts (W) or kilowatts (kW). This is the energy consumed by the resistive part of the circuit to perform work (e.g., producing heat, light, or mechanical torque).

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