*Question E5D12:
What is reactive power?*  

*Correct Answer is  D: Wattless, nonproductive power*  

### AI Response: (may contain errors)  

Reactive power is a concept in AC circuits that is important for understanding how energy is stored and released by inductors and capacitors. Let's break down the correct answer and why the other choices are incorrect:

### Correct Answer: D: Wattless, nonproductive power

- **Explanation**: Reactive power, measured in VARs (volt-amperes reactive), represents the power that oscillates between the source and reactive components (inductors and capacitors) in an AC circuit. It does not perform any real work, hence it is called "wattless" or "nonproductive" power. Reactive power is essential for maintaining voltage levels necessary for active power (real power) to do useful work.

### Why the Other Choices are Incorrect:

- **A: Power consumed in circuit Q**  
  - **Explanation**: This choice is misleading. Reactive power is not "consumed" in the circuit; rather, it is exchanged back and forth between the source and the reactive components. The term "circuit Q" typically refers to the quality factor of a circuit, not reactive power.

- **B: Power consumed by an inductor’s wire resistance**  
  - **Explanation**: This describes real power loss due to resistance in the inductor's wire, which is not reactive power. Real power is dissipated as heat and is measured in watts, not VARs.

- **C: The power consumed in inductors and capacitors**  
  - **Explanation**: Inductors and capacitors do not "consume" power in the sense of converting it to work or heat. They store and release energy, contributing to reactive power, but do not consume it like resistive elements do.

### Useful Formulas:

- **Apparent Power ($S$)**: The total power in an AC circuit, measured in volt-amperes (VA).
  $$ S = \sqrt{P^2 + Q^2} $$
  where:
  - $P$ = Real power (watts)
  - $Q$ = Reactive power (VARs)

- **Power Factor ($\text{pf}$)**: The ratio of real power to apparent power.
  $$ \text{pf} = \frac{P}{S} $$

Understanding these concepts helps in analyzing AC circuits and ensuring efficient power delivery.