*Question E4E05:
What is used to suppress radio frequency interference from a line-driven AC motor?*  

*Correct Answer is  B: A brute-force AC-line filter in series with the motor’s power leads*  

### AI Response: (may contain errors)  

To suppress radio frequency interference (RFI) from a line-driven AC motor, the correct answer is:

**B: A brute-force AC-line filter in series with the motor’s power leads.**

### Explanation of the Correct Answer:
- **Brute-force AC-line filter**: This type of filter is designed to attenuate high-frequency noise generated by the motor. It typically consists of inductors and capacitors that work together to block unwanted RF signals while allowing the desired AC power to pass through. This is effective in reducing RFI that can affect nearby radio equipment.

### Why the Other Choices are Incorrect:
- **A: A high-pass filter in series with the motor’s power leads**: 
  - A high-pass filter allows high-frequency signals to pass while attenuating low-frequency signals. This is not suitable for suppressing RFI from a motor, as the interference is typically at high frequencies, and a high-pass filter would not effectively block it.

- **C: A bypass capacitor in series with the motor’s field winding**: 
  - A bypass capacitor is used to shunt high-frequency noise to ground, but placing it in series with the field winding would block the AC current necessary for the motor to operate. Bypass capacitors are usually placed in parallel to ground for effective noise suppression.

- **D: A bypass choke in parallel with the motor’s field winding**: 
  - While a bypass choke can help reduce RFI, placing it in parallel with the field winding would not effectively suppress the interference. Instead, it could affect the motor's performance by limiting the current flow through the winding.

### Summary:
- The best method to suppress RFI from a line-driven AC motor is to use a brute-force AC-line filter in series with the motor’s power leads. This setup effectively reduces high-frequency noise while allowing the motor to function properly.