Class 4 (4th Engineer) MET 📅 May 2023

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 230. 50Hz supply, find the circuit current, the power factor and the power dissipation. (10)

Reference Answer

### Part (a): Explanation of Power Factor (6 Marks)
#### 1. Definition and Concept
Power Factor (PF) is a dimensionless quantity that measures 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. This is the power consumed by the resistive part of a circuit to perform work, such as creating heat, light, or mechanical torque. It is measured in Watts (W) or Kilowatts (kW).

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