Question

Which instrument can be used to measure potential difference across a resistor?

• A. Ammeter
• B. Voltmeter
• C. Galvanometer
• D. Potentiometer

Hint:

Always remember:
- Ammeter measures current and is connected in series.
- Voltmeter measures voltage and is connected in parallel.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to identify the standard laboratory instrument designed specifically to measure the electric potential difference across a resistor.

Step 2: Key Formula or Approach:
Analyze the purpose of each listed instrument:
- Ammeter: Measures electric current in amperes.
- Voltmeter: Measures potential difference in volts.
- Galvanometer: Detects the presence and direction of small electric currents.
- Potentiometer: A highly accurate null-method instrument used to measure EMF and compare internal resistances, but for direct measurement of potential difference in practical circuits, a voltmeter is standard.

Step 3: Detailed Explanation:

• A voltmeter is an instrument designed to measure the potential difference between two points in an electrical circuit.

• To measure the potential difference across a resistor, the voltmeter is connected in parallel with the resistor.

• It has a very high internal resistance so that it draws negligible current from the main circuit, ensuring that the circuit's operation and the voltage drop are not affected.

• This matches Option (B) as the direct measuring tool.


Step 4: Final Answer:
The instrument used to measure potential difference is a Voltmeter.