*Question G4B05:
Why do voltmeters have high input impedance?*  

*Correct Answer is  D: It decreases the loading on circuits being measured*  

### AI Response: (may contain errors)  

Voltmeters are designed with high input impedance primarily to minimize the impact they have on the circuit being measured. Let's break down the correct answer and the other choices:

### Correct Answer: D - It decreases the loading on circuits being measured

- **Explanation**: 
  - High input impedance means that the voltmeter draws very little current from the circuit. This is crucial because if a voltmeter had low input impedance, it would draw significant current, altering the voltage across the component being measured. This phenomenon is known as "loading," and it can lead to inaccurate readings. By having high input impedance, the voltmeter ensures that it does not affect the circuit's operation, allowing for a more accurate measurement of the voltage.

### Why the Other Choices are Incorrect:

- **A: It improves the frequency response**  
  - **Explanation**: While input impedance can affect frequency response, the primary reason for high input impedance in voltmeters is to reduce loading. Frequency response is more related to the design of the circuit and the components used rather than just the input impedance.

- **B: It allows for higher voltages to be safely measured**  
  - **Explanation**: The ability to measure higher voltages is more related to the design and insulation of the voltmeter rather than its input impedance. High input impedance does not inherently allow for higher voltage measurements; it simply means that the voltmeter will not load the circuit.

- **C: It improves the resolution of the readings**  
  - **Explanation**: Resolution refers to the smallest change in voltage that can be detected by the voltmeter. While high input impedance can contribute to better accuracy, it does not directly improve resolution. Resolution is more dependent on the internal design and digitization of the voltmeter.

### Summary

- High input impedance is essential for voltmeters to minimize circuit loading and ensure accurate voltage measurements.
- The other options do not accurately reflect the primary purpose of high input impedance in voltmeters. 

This understanding is crucial for the Extra Class exam, as it highlights the importance of measurement tools in circuit analysis.