Question

For measuring the voltage of any circuit, a potentiometer is preferred to a voltmeter because
(A) The potentiometer is cheap and easy to handle.
(B) Calibration in voltmeter is sometimes wrong.
(C) The potential draws no current during measurement.
(D) Range of the voltmeter is not as wide as that of the potentiometer.

Answer 1

Hint: A potentiometer is a voltage divider that is used to measure the electric potential difference or voltage across two points in an electric circuit. During the measurement of voltage, some amount of current has been drawn from the device. This would affect the accuracy of the device.

Complete step by step answer:
For measuring the voltage of any circuit, a potentiometer is preferred to a voltmeter because a voltmeter draws a certain current from the circuit for its own operation whereas no such current is drawn by the potentiometer for its working.

$\therefore $ Hence, the correct option is (C) is correct.

Additional information:
(i) The potentiometer consists of a three-terminal resistor along with a sliding or rotating contact which forms a voltage divider that is adjustable. A potentiometer can act as a variable resistor (rheostat) if instead of a three-terminal resistor; a two-terminal resistor is being used.
(ii) A potentiometer measures the voltage or 'potential difference' by comparing an unknown voltage with a known reference voltage. In this, a sensitive indicating instrument like a galvanometer is used so that very little current is drawn from the voltage of an unknown source. As the reference voltage is produced from an accurately calibrated voltage divider, the potentiometer provides measurement with higher precision.
(iii) A voltmeter like a potentiometer is also used to measure the electric potential difference across two points in an electric circuit. A voltmeter is of two types i.e. analog voltmeter and digital voltmeter. In an Analog voltmeter, the pointer moves in the scale in proportion to the voltage moving across the electric circuit; whereas a digital voltmeter displays a numerical value of the voltage with the help of an analog-to-digital converter.

Note:
A voltmeter for its working draws some current from the electric circuit due to which its measurement is not accurate. Therefore, often a galvanometer is converted into a voltmeter by connecting a resistor in series with the galvanometer so that the instrument disturbs the circuit as less as possible thus drawing minimum current out of the circuit for its own functioning.