Question

State the advantages of potentiometer over voltmeter.

Answer 1

Hint: Here, in this question first we will see the basic uses of the potentiometer and voltmeter and then we will see the advantages of potentiometer over the voltmeter. Both of them have advantage in different uses.

Complete step-by-step answer:
We already know that a potentiometer is a null method device. At this null point it does not draw any current from the cell and therefore, there is no potential drop due to the internal resistance of the cell. A voltmeter is a device that is used for measuring electric potential difference between two points in an electric circuit.
1) Potentiometer measures the potential difference in an open circuit which is equal to the actual e.m.f of the cell. Furthermore, potentiometer gives the exact value of potential difference across any two points in a given circuit because as we know it never draws any current from the circuit whereas, the voltmeter draws a part of the current so there is an error in measurement of the potential difference by the voltmeter. Also, we can say that voltmeter measures the terminal potential difference in a closed circuit which is less than the e.m.f of a cell. This is the reason why a potentiometer is preferred over a voltmeter for measuring the e.m.f. of a cell.
2) Potentiometer can be used for measuring the internal resistance of a cell and also compare the e.m.f. of two cells. Further, we can also measure any physical quantity that can produce or control a potential difference, using a potentiometer, which cannot be done using a Voltmeter.

Additional Information: The potential difference is defined as the measure between any two points A and B. It can be defined as the change in potential energy of a charge q when moved from point A to point B, divided by the charge. Potential difference is measured in joules per coulomb, which is given as volt (V). This name of the unit is given in the name after Alessandro Volta.

Note: We should remember that both the potentiometer and voltmeter are important in their own aspects. Potentiometer acts as an adjustable voltage divider. There are digital voltmeters which give us numerical display of voltage by use of an analog-to-digital converter.