Question

Why do we prepare a potentiometer to measure the emf of a cell rather than a voltmeter?

Answer 1

Hint: As the potentiometer does not draw any current for itself from the primary circuit. As a result, it provides more precise readings, making it an ideal voltmeter. Voltmeters, on the other hand, draw a significant amount of current, which is insufficient for measuring the emf of a cell.

Complete answer:
We prepare a potentiometer to measure the emf of a cell rather than a voltmeter because a voltmeter has a limited resistance and pulls current from a cell, it measures terminal potential difference rather than emf, whereas a potentiometer, when in balance, does not draw any current from the cell, leaving the cell open circuit. As a result, the true value of emf is read by the potentiometer.
A voltage divider made up of a three-terminal resistor and a sliding or rotating contact is known as a potentiometer. It operates as a variable resistor or rheostat when only two terminals, one end and the wiper, are employed.
A potentiometer is a voltage divider that is used to monitor electric potential (voltage); the component's name comes from the same idea.
Potentiometers are often used to operate electrical devices, such as audio equipment volume controls. In a joystick, for example, potentiometers operated by a mechanism can be used as position transducers. Potentiometers are rarely used to directly regulate significant power since the power dissipated in the potentiometer is comparable to the power dissipated in the controlled load (greater than a watt).

Note:
Potentiometers control the position of a sliding contact across a uniform resistance by changing its location. The full input voltage is applied over the entire length of the resistor in a potentiometer, and the output voltage equals the difference between the fixed and sliding contacts.