*Question E4A10:
Which trigger mode is most effective when using an oscilloscope to measure a linear power supply’s output ripple?*  

*Correct Answer is  D: Line*  

### AI Response: (may contain errors)  

To measure a linear power supply's output ripple effectively using an oscilloscope, the best trigger mode is **Line**. Here's why:

### Correct Answer: Line
- **Line Trigger Mode**: This mode synchronizes the oscilloscope's triggering to the AC line frequency (typically 50 or 60 Hz). Since most linear power supplies operate by rectifying AC voltage, the ripple frequency will be related to the line frequency. By using the line trigger, you can stabilize the waveform on the screen, making it easier to observe the ripple voltage superimposed on the DC output.

### Why Other Choices Are Incorrect:
- **A: Single-shot**: 
  - This mode captures a single event and is not suitable for repetitive waveforms like the ripple from a power supply. It may not provide a stable display of the ripple since it does not continuously trigger on the waveform.

- **B: Edge**: 
  - Edge triggering is useful for capturing waveforms based on a specific voltage level crossing (rising or falling edge). However, it may not provide a stable view of the ripple if the waveform is not periodic or if the ripple frequency is not synchronized with the triggering.

- **C: Level**: 
  - Level triggering requires the signal to cross a specified voltage level to trigger the oscilloscope. Similar to edge triggering, it may not effectively stabilize the ripple waveform, especially if the ripple amplitude varies.

### Summary
Using the **Line** trigger mode allows you to effectively measure and analyze the ripple voltage of a linear power supply by synchronizing the oscilloscope to the AC line frequency, ensuring a stable and clear display of the waveform. 

### Useful Rule of Thumb
- For measuring ripple or periodic signals, always consider using a trigger mode that matches the frequency of the signal you are observing, such as line triggering for power supply ripple.