Question

What are the three types of power used in AC circuits?

Answer 1

In AC (alternating current) circuits, three main types of power are used to describe how energy flows and is consumed. These are:

1. Active Power (Real Power) – \(P\)

   - Unit: Watts (W)
   - Description: This is the power that actually does useful work in the circuit, such as lighting a bulb or turning a motor. It's the "real" power that is consumed and converted into other forms of energy (like heat, light, or mechanical energy).
   - Formula: \( P = V \times I \times \cos(\theta) \)
     - Where \(V\) is voltage, \(I\) is current, and \(\theta\) is the phase difference between voltage and current.

2. Reactive Power – \(Q\)

   - Unit: Volt-Amps Reactive (VAR)
   - Description: This power does not perform any real work but is necessary for creating magnetic and electric fields in inductive and capacitive components (like motors, transformers, and capacitors). It "oscillates" between the source and the load, storing energy temporarily and then releasing it.
   - Formula: \( Q = V \times I \times \sin(\theta) \)

3. Apparent Power – \(S\)

   - Unit: Volt-Amps (VA)
   - Description: This is the total power supplied to the circuit, combining both active and reactive power. It's the vector sum of active and reactive power and represents the overall demand from the source.
   - Formula: \( S = V \times I \)
     - Or, in terms of active and reactive power: \( S = \sqrt{P^2 + Q^2} \)

These three powers are related through the power factor (PF), which is the ratio of active power to apparent power:

\[
\text{Power Factor} = \frac{P}{S} = \cos(\theta)
\]

Where \(\theta\) is the phase angle between voltage and current.

To summarize:

1. Active Power (P) does useful work.
   

1. Reactive Power (Q) supports the system but doesn't do useful work.
   

1. Apparent Power (S) is the total power drawn from the supply.
   

Let me know if you'd like further clarification on any of these!