Question

The device used for measuring potential difference is known as
A. Galvanometer
B. Ammeter
C. Voltmeter
D. Potentiometer

Answer 1

To measure the potential difference, the terminals of measuring instruments should be connected across the component where we expect drop in the voltage. Also, since we have connected the measuring device across the electric component, the current should not be drawn by the measuring device to measure potential difference. Recall such an electric measurement device.

Complete answer:
The device used to measure potential difference across the electric component must not draw any current through the circuit. To do so, the resistance of the measuring instruments must be very high. To answer this question, let’s check every given option.

Galvanometer:
We know that the galvanometer is a measuring device which measures a small current passing through the circuit if any. It is always placed in series with the circuit. We know that for the measuring instruments to measure the potential difference across the electric component, it should be connected across that component. In this way, the measuring device can measure the drop in the voltage across the electric component.
Therefore, the option (A) is incorrect.

Ammeter:
We know that ammeter measures electric current in the circuit and it is always connected in series. Therefore, the option (B) is incorrect.

Voltmeter:
We know that voltmeter is always connected across the electric component to measure the voltage drop across that component. Drop or rise in the voltage is known as potential difference. Therefore, we can say that voltmeter measures electric potential difference.

Potentiometer:
We know that the potentiometer is a device used as a voltage divider in the circuit to bring down the voltage to a desired value. It is generally used to measure the emf of the cell. Therefore, the option (D) is incorrect.

So, the correct answer is option (C).

Note: Potentiometer can also measure the potential difference but it is not generally used to measure the potential difference rather used to provide a desired value of voltage at the load by knob control. To answer such types of questions, the key is to remember how the measuring instruments are connected in the circuit and the resistance of the measuring device.