*Question T6D03:
Which of the following is a reason to use shielded wire?*  

*Correct Answer is  C: To prevent coupling of unwanted signals to or from the wire*  

### AI Response: (may contain errors)  

To understand why the correct answer is C, let's break down the reasoning:

### Correct Answer: C
**To prevent coupling of unwanted signals to or from the wire.**

- **Explanation**: Shielded wire is designed to protect the internal conductor from external electromagnetic interference (EMI). The shield, typically made of conductive material, acts as a barrier that absorbs and redirects unwanted signals, preventing them from coupling into the wire. This is particularly important in radio frequency (RF) applications where noise can significantly affect signal quality.

### Why the Other Choices are Incorrect:

- **A: To decrease the resistance of DC power connections**  
  - **Explanation**: Shielded wire does not inherently decrease the resistance of the wire. The resistance is primarily determined by the wire's material and cross-sectional area. Shielding is focused on signal integrity rather than resistance.

- **B: To increase the current carrying capability of the wire**  
  - **Explanation**: The current carrying capability of a wire is determined by its gauge (thickness) and material. Shielding does not increase this capability; it is primarily for signal protection.

- **D: To couple the wire to other signals**  
  - **Explanation**: Shielded wire is used to prevent coupling of unwanted signals, not to facilitate it. The purpose of the shield is to isolate the internal conductor from external signals, ensuring that only the intended signals are transmitted.

### Summary
- Shielded wire is essential for maintaining signal integrity by preventing unwanted interference.
- The other options do not accurately describe the primary function of shielded wire.

This understanding is crucial for the Extra Class exam, as it highlights the practical applications of different types of wiring in amateur radio setups.