Physics Practicals Class 12

Potentiometer – Comparison of EMF of Cells

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About Simulation

  • In this simulation, you will learn about the potentiometer apparatus and its components.
  • You will learn about the balancing principle of the potentiometer and compare the EMF of cells.
  • You will repair the potentiometer of machine in the factory and get more information about the potentiometer.
  • All the potentiometer experiment steps and procedures like connecting wires, observing galvanometer deflections, measuring the balancing length, noting down the readings, etc., are highly interactive and have been simulated in a very similar manner as you do in a real lab.


  • This interaction provides a very immersive virtual reality environment and gives you a real-lab-like experience while conducting or performing experiments.
  • It is one of the important class 12 physics practicals that you can learn in our virtual lab.

Simulation Details

Duration – 30 Minutes
Easily Accessible
Language – English
Platforms – Android & Windows


The potentiometer is a device that is used to compare the EMF (electromotive force) of two cells, to measure the internal resistance of a cell, and the potential difference across a resistor. It consists of a long wire (10m) with having a uniform cross-sectional area. The material of the wire should have a high resistivity and low-temperature coefficient.

The potentiometer works on the principle that when a constant current flows through a wire of uniform cross-sectional area, the potential difference between its two points is directly proportional to the length of the wire between the two points.

Electromotive force (EMF) is a measurement of the energy that causes current to flow through a circuit. It is the energy provided by a cell or battery per coulomb of charge passing through it. It can also be defined as the potential difference across the terminals of a cell when no current flows through it. Electromotive force is also known as voltage, and it is measured in volts.

Using a potentiometer, we can determine the emf of a cell by obtaining the balancing length 𝑙. Here, the fall of potential along the length 𝑙 of the potentiometer wire is equal to the EMF of the cell, as no current is being drawn from the cell.

Then, $$E \propto l \text{ or } E=k l$$

Where, 𝑘 is the potential gradient along the wire.

Thus, it is possible to compare the EMF of two given cells by measuring the respective balancing lengths 𝑙1 and 𝑙2. $$\frac{E_1}{E_2}=\frac{l_1}{l_2}$$

Requirements for this Science Experiment

Potentiometer Leclanché Cell, Daniel Cell Resistance Box Jockey Galvanometer Ammeter Galvanometer Plug Key

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