*Question E5C05:
What kind of diagram is used to show the phase relationship between impedances at a given frequency?*  

*Correct Answer is  C: Phasor diagram*  

### AI Response: (may contain errors)  

To understand the correct answer to this question, let's break down the options:

### Correct Answer: C - Phasor Diagram

- A **phasor diagram** is a graphical representation used in electrical engineering to illustrate the phase relationships between alternating current (AC) voltages and currents. 
- In a phasor diagram, each quantity is represented as a vector (or phasor) that rotates in a circular motion, with the angle representing the phase difference. This is particularly useful for analyzing circuits at a specific frequency, as it allows for easy visualization of how different impedances relate to each other in terms of both magnitude and phase.

### Why the Other Choices are Incorrect:

- **A: Venn Diagram**
  - A Venn diagram is used to show the relationships between different sets, typically in mathematics and logic. It does not represent phase relationships or electrical concepts.

- **B: Near Field Diagram**
  - A near field diagram is used to describe the electromagnetic field close to an antenna. It does not specifically illustrate phase relationships between impedances.

- **D: Far Field Diagram**
  - A far field diagram represents the electromagnetic field at a distance from the antenna, focusing on radiation patterns rather than phase relationships between impedances.

### Useful Concepts:

- **Impedance ($Z$)** is a complex quantity that combines resistance ($R$) and reactance ($X$):
  $$Z = R + jX$$
  where $j$ is the imaginary unit.

- **Phase Angle ($\phi$)** can be calculated from the impedance:
  $$\phi = \tan^{-1}\left(\frac{X}{R}\right)$$
  This angle is crucial in phasor diagrams as it indicates the phase difference between voltage and current.

Understanding these concepts will help you visualize and analyze AC circuits effectively, especially when preparing for the Extra Class exam.