Which arrangement describes the correct method to measure the potential difference across a single resistor?

Which arrangement describes the correct method to measure the potential difference across a single resistor?

• A. Connect the voltmeter in parallel with the resistor
• B. Connect the voltmeter in series with the resistor
• C. Connect the voltmeter across the power supply only
• D. Connect the voltmeter across the entire circuit

Answer: (A)

To measure the potential difference across a single resistor, connect the voltmeter in parallel with the resistor. A voltmeter measures the difference in electric potential between two points, and placing it across the resistor allows it to read the exact voltage drop across that component while drawing minimal current because of its high internal resistance. If the voltmeter were placed in series, it would become part of the current path and distort the circuit, giving an incorrect reading of the resistor’s drop. Measuring across the power supply would show the supply voltage, not the resistor’s drop, and measuring across the entire circuit would reflect the total circuit voltage rather than the specific resistor.

To measure the potential difference across a single resistor, connect the voltmeter in parallel with the resistor. A voltmeter measures the difference in electric potential between two points, and placing it across the resistor allows it to read the exact voltage drop across that component while drawing minimal current because of its high internal resistance. If the voltmeter were placed in series, it would become part of the current path and distort the circuit, giving an incorrect reading of the resistor’s drop. Measuring across the power supply would show the supply voltage, not the resistor’s drop, and measuring across the entire circuit would reflect the total circuit voltage rather than the specific resistor.