*Question G5A11:
What letter is used to represent reactance?*  

*Correct Answer is  B: X*  

### AI Response: (may contain errors)  

The correct answer to the question about the letter used to represent reactance is **B: X**.

### Explanation of the Correct Answer:
- **Reactance** is a measure of how much a circuit resists the flow of alternating current (AC) due to capacitance or inductance. 
- In electrical engineering, reactance is denoted by the letter **X**. 
- It can be further classified into:
  - **Inductive Reactance ($X_L$)**: Represented as $X_L = 2 \pi f L$, where:
    - $f$ = frequency in hertz
    - $L$ = inductance in henries
  - **Capacitive Reactance ($X_C$)**: Represented as $X_C = \frac{1}{2 \pi f C}$, where:
    - $C$ = capacitance in farads

### Why the Other Choices are Incorrect:
- **A: Z**: This letter represents **impedance**, which is the total opposition to current flow in an AC circuit, combining both resistance and reactance. It is not specific to reactance alone.
  
- **C: B**: This letter is not commonly used in electrical engineering to represent any specific quantity related to reactance or impedance.
  
- **D: Y**: This letter represents **admittance**, which is the measure of how easily a circuit allows current to flow, and is the reciprocal of impedance. It does not denote reactance.

### Summary:
- Reactance is denoted by **X**.
- Impedance is denoted by **Z**.
- Admittance is denoted by **Y**.
- The correct answer is **B: X** because it specifically represents reactance in electrical circuits.