*Question E6D06:
What core material property determines the inductance of an inductor?*  

*Correct Answer is  D: Permeability*  

### AI Response: (may contain errors)  

The correct answer is **D: Permeability**.

### Explanation:

1. **Why the correct answer is correct:**
   - **Permeability** is a property of a material that indicates how well it can support the formation of a magnetic field within itself. It directly affects the inductance of an inductor. The inductance \( L \) of an inductor is given by the formula:
     $$ L = \frac{{N^2 \cdot \mu \cdot A}}{{l}} $$
     where:
     - \( N \) = number of turns in the coil
     - \( \mu \) = permeability of the core material
     - \( A \) = cross-sectional area of the core
     - \( l \) = length of the coil
   - Higher permeability means the material can support a stronger magnetic field, resulting in higher inductance.

2. **Why the other choices are incorrect:**
   - **A: Permittivity**: This property relates to how a material affects electric fields and is relevant to capacitors, not inductors. It does not determine inductance.
   - **B: Resistance**: This is a measure of how much a material opposes the flow of electric current. While resistance affects the efficiency of an inductor, it does not determine its inductance.
   - **C: Reactivity**: This is not a material property but rather a term related to the opposition to changes in current or voltage in reactive components like inductors and capacitors. It does not determine inductance.

By understanding these properties, you can see why permeability is the key factor in determining the inductance of an inductor.