*Question E5D10:
As a conductor’s diameter increases, what is the effect on its electrical length?*  

*Correct Answer is  D: It increases*  

### AI Response: (may contain errors)  

As a conductor's diameter increases, its electrical length increases. Here's why:

1. **Why the correct answer is correct (D: It increases):**
   - The electrical length of a conductor is influenced by its physical length and the velocity factor, which is affected by the conductor's diameter. A larger diameter reduces the inductance per unit length and increases the capacitance per unit length. This results in a slower propagation velocity of the signal along the conductor, effectively increasing its electrical length.

2. **Why the other choices are incorrect:**
   - **A: Thickness has no effect on electrical length**  
     This is incorrect because the diameter of the conductor does affect the velocity factor, which in turn affects the electrical length.
   - **B: It varies randomly**  
     This is incorrect because the relationship between diameter and electrical length is not random; it follows predictable electromagnetic principles.
   - **C: It decreases**  
     This is incorrect because, as explained, increasing the diameter actually increases the electrical length due to changes in inductance and capacitance.

3. **Useful formulas or rules of thumb:**
   - The electrical length \( L_e \) can be expressed as:  
     $$ L_e = \frac{L_p}{v_f} $$
     where:
     - \( L_p \) = physical length of the conductor
     - \( v_f \) = velocity factor, which decreases as the diameter increases

Understanding these principles helps in designing antennas and transmission lines where the electrical length is a critical parameter.