*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 to the question about the core material property that determines the inductance of an inductor is **D: Permeability**.

### Explanation of the Correct Answer:
- **Permeability ($\mu$)** is a measure of how easily a magnetic field can penetrate a material. It directly affects the inductance of an inductor, which is given by the formula:

$$
L = \frac{N^2 \mu A}{l}
$$

where:
- $L$ = inductance in henries (H)
- $N$ = number of turns in the coil
- $A$ = cross-sectional area of the core in square meters (m²)
- $l$ = length of the coil in meters (m)

From this formula, you can see that higher permeability increases the inductance.

### Why the Other Choices are Incorrect:
- **A: Permittivity**: This property relates to how an electric field interacts with a dielectric material. It does not influence the inductance of an inductor, which is primarily concerned with magnetic fields.

- **B: Resistance**: While resistance affects the efficiency of an inductor (losses due to heat), it does not determine the inductance itself. Inductance is a function of the magnetic properties of the core material, not its resistance.

- **C: Reactivity**: This term generally refers to the opposition of a circuit to changes in current or voltage due to inductance and capacitance. It is not a property of the core material that determines inductance.

### Summary:
- The inductance of an inductor is primarily determined by the **permeability** of the core material, which enhances the magnetic field within the inductor. Other properties like permittivity, resistance, and reactivity do not directly influence inductance.