Learning Objectives:

- Understand the concept of AC power
- Understand the difference between real power, reactive power, and apparent power
- Understand how to measure AC power using a power meter

Introduction: In AC circuits, power is constantly changing due to the alternating nature of the current and voltage. Therefore, it is important to understand the concept of AC power and its measurement. AC power has three components: real power, reactive power, and apparent power.

AC Power Components: Real power, also known as active power, is the power consumed by the circuit that performs useful work, such as turning a motor or lighting a bulb. It is measured in watts (W). Reactive power is the power consumed by the circuit due to inductors and capacitors, which store and release energy in the circuit. It is measured in volt-amperes reactive (VAR). Apparent power is the combination of real and reactive power, and it is the total power that the circuit draws from the source. It is measured in volt-amperes (VA).

AC Power Measurement: To measure AC power, a power meter is used. A power meter measures the voltage and current in the circuit and calculates the power based on the following formula:

Real Power (P) = Voltage (V) x Current (I) x Power Factor (PF)

The power factor is a measure of how efficiently the circuit is using the power. It is the ratio of real power to apparent power, and it is typically between 0 and 1. A power factor of 1 means that all the power drawn by the circuit is used for useful work, while a power factor less than 1 means that some of the power is being wasted due to inefficiencies in the circuit.

Example Calculation: Suppose a motor is rated at 240 volts and draws a current of 10 amperes with a power factor of 0.8. To calculate the real power consumed by the motor, we can use the formula:

Real Power (P) = Voltage (V) x Current (I) x Power Factor (PF) P = 240 x 10 x 0.8 = 1,920 watts

Conclusion: AC power is an important concept in AC circuits. It has three components: real power, reactive power, and apparent power. Real power is the power consumed by the circuit that performs useful work, while reactive power is the power consumed by the circuit due to inductors and capacitors, and apparent power is the total power drawn by the circuit from the source. To measure AC power, a power meter is used, which calculates the power based on the voltage, current, and power factor of the circuit.