*Question G6B10:
How does a ferrite bead or core reduce common-mode RF current on the shield of a coaxial cable?*  

*Correct Answer is  A: By creating an impedance in the current’s path*  

### AI Response: (may contain errors)  

To understand how a ferrite bead or core reduces common-mode RF current on the shield of a coaxial cable, let's break down the correct answer and the other options.

### Correct Answer: A - By creating an impedance in the current’s path

- **Explanation**: Ferrite beads and cores are made from materials that have high magnetic permeability. When common-mode RF currents flow through the coaxial cable, the ferrite creates a high impedance to these currents. This impedance effectively resists the flow of the unwanted common-mode currents while allowing the differential mode signals (the intended signals) to pass through with minimal attenuation. The result is a reduction in RF interference and noise.

### Why the Other Choices are Incorrect:

- **B: It converts common-mode current to differential mode current**  
  - **Explanation**: Ferrite beads do not convert common-mode currents into differential mode currents. Instead, they suppress common-mode currents by providing impedance. The distinction is important: they do not change the type of current but rather impede its flow.

- **C: By creating an out-of-phase current to cancel the common-mode current**  
  - **Explanation**: While out-of-phase currents can cancel each other, ferrite beads do not generate out-of-phase currents. They simply provide a resistive path that reduces the amplitude of the common-mode current without creating a counteracting current.

- **D: Ferrites expel magnetic fields**  
  - **Explanation**: This statement is misleading. Ferrites do not expel magnetic fields; rather, they absorb and dissipate energy from the magnetic fields associated with RF currents. Their function is to increase impedance to RF currents, not to expel magnetic fields.

### Summary

- Ferrite beads and cores work by creating impedance in the path of common-mode currents, effectively reducing their amplitude and minimizing interference.
- Understanding the role of ferrite materials is crucial for effective RF design and noise reduction in amateur radio setups. 

This knowledge will help you answer similar questions on the Extra Class exam.