*Question E9H10:
How can the output voltage of a multiple-turn receiving loop antenna be increased?*  

*Correct Answer is  C: By increasing the number of turns and/or the area enclosed by the loop*  

### AI Response: (may contain errors)  

To increase the output voltage of a multiple-turn receiving loop antenna, you can:

### Correct Answer: C
**By increasing the number of turns and/or the area enclosed by the loop**

1. **Explanation:**
   - The output voltage of a loop antenna is proportional to the rate of change of magnetic flux through the loop. This can be increased by:
     - **Increasing the number of turns ($N$):** More turns mean more wire is cutting through the magnetic field, which increases the induced voltage.
     - **Increasing the area ($A$) enclosed by the loop:** A larger area captures more of the magnetic field, increasing the magnetic flux and thus the induced voltage.

2. **Formula:**
   - The induced voltage ($V$) in a loop is given by Faraday's Law of Induction:
     $$ V = -N \frac{d\Phi}{dt} $$
   - Where $\Phi$ is the magnetic flux, $N$ is the number of turns, and $\frac{d\Phi}{dt}$ is the rate of change of magnetic flux.

### Incorrect Choices:

**A: By reducing the permeability of the loop shield**
- **Explanation:** Reducing the permeability of the loop shield would actually decrease the efficiency of the loop in capturing magnetic fields, thus reducing the output voltage. Permeability is a measure of how easily a material can support the formation of a magnetic field within itself.

**B: By utilizing high impedance wire for the coupling loop**
- **Explanation:** The impedance of the wire affects the current flow but does not directly increase the induced voltage. High impedance wire might affect the matching and efficiency but not the fundamental voltage induced by the magnetic field.

**D: All these choices are correct**
- **Explanation:** Since choices A and B are incorrect, this option is also incorrect. Only increasing the number of turns and/or the area enclosed by the loop will increase the output voltage.