*Question E6D11:
Which type of core material decreases inductance when inserted into a coil?*  

*Correct Answer is  B: Brass*  

### AI Response: (may contain errors)  

To understand which type of core material decreases inductance when inserted into a coil, we need to consider how different materials affect the magnetic field within the coil.

### Correct Answer: Brass

- **Why Brass is Correct:**
  - Brass is a non-magnetic metal. When inserted into a coil, it does not enhance the magnetic field, and in fact, it can disrupt the magnetic lines of force. This disruption leads to a decrease in inductance. Inductance is influenced by the permeability of the core material, and since brass has low permeability, it reduces the inductance.

### Why the Other Choices are Incorrect:

- **A: Ceramic**
  - Ceramic materials are often used as insulators and can have high permeability, depending on their composition. They generally do not decrease inductance; instead, they can maintain or slightly increase it.

- **C: Ferrite**
  - Ferrite is a magnetic material with high permeability. When inserted into a coil, ferrite increases the inductance by enhancing the magnetic field. This is the opposite of what we are looking for.

- **D: Aluminum**
  - Aluminum is also a non-magnetic metal, but it has some conductivity. While it may not significantly increase inductance like ferrite, it does not decrease it as effectively as brass does. It can create eddy currents that may affect the coil's performance but does not lead to a decrease in inductance.

### Summary:
- Inductance decreases with materials that have low permeability, like brass.
- Inductance increases with materials that have high permeability, like ferrite.

### Useful Rule of Thumb:
- **Core Material Impact on Inductance:**
  - Non-magnetic materials (e.g., brass) can decrease inductance.
  - Magnetic materials (e.g., ferrite) can increase inductance. 

This understanding is crucial for selecting materials in RF applications and designing inductive components.