*Question E5D06:
What parasitic characteristic creates an inductor’s self-resonance?*  

*Correct Answer is  D: Inter-turn capacitance*  

### AI Response: (may contain errors)  

To understand the self-resonance of an inductor, we need to focus on the parasitic characteristics that affect its behavior. 

### Correct Answer: Inter-turn capacitance

- **Inter-turn capacitance** refers to the capacitance that exists between the turns of wire in an inductor. This capacitance can create a resonant circuit when combined with the inductance of the coil. At a certain frequency, the inductive reactance and capacitive reactance can cancel each other out, leading to self-resonance. 

### Why the other choices are incorrect:

- **A: Skin effect**  
  - The skin effect is the tendency of alternating current (AC) to distribute itself within a conductor such that the current density is largest near the surface and decreases with greater depth. While it affects the effective resistance of the inductor at high frequencies, it does not contribute to self-resonance.

- **B: Dielectric loss**  
  - Dielectric loss refers to the energy lost as heat in the insulating material between the turns of the inductor. While it can affect the quality factor (Q) of the inductor, it does not create self-resonance.

- **C: Coupling**  
  - Coupling generally refers to the interaction between two inductors or circuits. While it can affect the performance of inductors in a circuit, it does not directly relate to the self-resonance of a single inductor.

### Useful Concepts:

- The self-resonant frequency ($f_{SR}$) can be approximated using the formula:

$$
f_{SR} = \frac{1}{2\pi\sqrt{L \cdot C}}
$$

where:
- $L$ = inductance in henries
- $C$ = inter-turn capacitance in farads

This formula shows how the inductance and inter-turn capacitance interact to determine the frequency at which self-resonance occurs. Understanding this relationship is crucial for designing inductors that operate effectively at specific frequencies.