Deep Dive: G4B05
The correct answer is D: It decreases the loading on circuits being measured. Why voltmeters have high input impedance is to decrease the loading on circuits being measured. High impedance means the voltmeter draws very little current, so it doesn't affect the circuit being measured. For amateur radio operators, this ensures accurate voltage measurements. Understanding this helps when using voltmeters.
Why Other Answers Are Wrong
Option A: Incorrect. High impedance doesn't improve frequency response - frequency response depends on the meter's design, not just impedance. Impedance affects loading, not frequency response. Option B: Incorrect. High impedance doesn't allow higher voltages to be safely measured - voltage ratings depend on insulation and design, not just impedance. Safety isn't about impedance. Option C: Incorrect. High impedance doesn't improve resolution - resolution depends on the meter's design and display, not just impedance. Resolution isn't about impedance.
Exam Tip
Voltmeter high impedance = decreases loading on circuits. Think 'H'igh 'I'mpedance = 'H'elps 'I'solate (doesn't load circuit). High impedance means voltmeter draws little current, so it doesn't affect circuit being measured. Not frequency response, not safety, not resolution - just loading.
Memory Aid
Voltmeter high impedance = decreases loading on circuits. Think 'H'igh 'I'mpedance = 'H'elps 'I'solate. High impedance means voltmeter draws little current, so it doesn't affect circuit being measured. Ensures accurate voltage measurements.
Real-World Example
You measure voltage in a high-impedance circuit. A voltmeter with high input impedance draws very little current, so it doesn't load the circuit and affect the voltage. A low-impedance voltmeter would draw significant current, loading the circuit and giving inaccurate readings. High impedance ensures accurate measurements.
Source & Coverage
Question Pool: 2023-2027 Question Pool
Subelement: G4B
Reference: 2023-2027 Question Pool · G4 - Amateur Radio Practices
Key Concepts
Verified Content
Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G4B topic.