EMF of a Cell Definition, Formulas, Calculation, and it’s Methods

Most students are unfamiliar with the idea of electromotive force, or EMF. However, it is inextricably tied to the more well-known idea of voltage. Understanding the differences between the two and what EMF stands for provides us with the skills we need to address a variety of physics and electronics challenges. It will also cover the concept of a battery’s internal resistance. The EMF indicates the voltage of the battery without taking into account the internal resistance. The emf formula will be explained with examples in this article. Let’s learn it together!

What is the electromagnetic field (EMF)?

When there is no current flowing through the battery, the electromotive force is defined as the potential difference across the terminals. Although it may not appear as if it makes a difference, every battery has internal resistance. It’s comparable to typical resistance in that it lowers current in a circuit, but it’s found inside the battery.

The energy delivered by a battery or a cell per coulomb (Q) of charge travelling through it is known as the electromotive force. When there is no current flowing through the circuit, the amount of emf is equal to V (potential difference) across the cell terminals

What is the distinction between EMF and Potential Difference?

EMF is the amount of energy converted into electrical energy per coulomb of charge. The potential difference, on the other hand, is the amount of electrical energy converted into other kinds of energy per coulomb of charge. Sources of emf include a cell, a solar cell, a battery, a generator, a thermocouple, a dynamo, and so on.

The EMF Formula is a formula that is used to calculate the EMF.

To compute EMF, there are two primary equations. The quantity of joules of energy that each coulomb of charge absorbs as it goes through the cell is the basic definition.

ε=E/Q

ε = emf (electromotive force) 

E  = Circuit’s energy.

Q = Circuit’s Charge

We can calculate the resulting energy and the amount of charge flowing through the cell if we know the resultant energy and the amount of charge passing through the cell. It is the most straightforward method of calculating the EMF.

Instead, we can use the definition V = IR, which is similar to Ohm’s law. So here’s the formula:

ε=IR+Ir

ε=V+Ir

I = Current

The cell’s electromotive force.

In the circuit, R = resistance.

r=  Cell’s internal resistance.

V= Voltage

This demonstrates that if we know the voltage across the terminals, the current flowing, and the cell’s internal resistance, we can compute the EMF.

A Cell’s EMF

The electromotive force of the cell, also known as the EMF, is the highest potential difference that exists between the two electrodes of a cell. The net voltage between the oxidation and reduction half-reactions is also known as this.

Electrochemical Cell Types

Galvanic Cell (Galvanic Cell)

A galvanic cell, also known as a voltaic cell, is a device that uses a spontaneous redox reaction to create electricity.

The reaction of zinc metal with aqueous copper sulphate solution is employed in this experiment.

Zn(s)+Cu²⁺(aq)→Zn²⁺(aq)+Cu(s)

It is made up of a zinc Electrode and a copper Electrode that have been bathed in zinc sulphate and copper sulphate solutions, respectively. The anode is the zinc electrode, and the cathode is the copper electrode. A zinc metal rod (anode) is immersed in a zinc sulphate solution in the container on the left. The copper rod (cathode) is immersed in a copper sulphate solution in the container on the right. The zinc and copper electrodes are connected by a copper connection. A salt bridge connects the solution in the anode and cathode compartments to the potassium sulphate solution.

In the anode compartment, the oxidation half-reaction occurs.

Zn(s)→Zn²⁺(aq)+2e⁻

The cathode reaction takes place as follows:

Cu²⁺(aq)+2e⁻→Cu(s)

Electrons are transferred from the zinc electrode to the copper cathode. Zn²⁺ is formed when zinc dissolves in the anode solution.

In a cathode half cell, ions absorb electrons and transform them to Cu atoms. Simultaneously, SO₄^2-

ions travel from the cathode half cell to the anode half cell through the salt bridge. Zn²⁺ is a similar case.

From the anode half cell to the cathode half cell, ions travel. Ions are transferred from one half-cell to the other to complete the circuit, ensuring a steady power source. The cell will keep running until either the zinc metal or the copper ions are depleted.

Daniel Cell 

It’s the same thing as a Galvanic Cell. The Copper-Zinc cell is also the same as the Galvanic Cell. The only difference is that Daniel’s cell can only use Zinc and Copper as Electrodes, whereas Galvanic cells can use a variety of metals as Electrodes.

The electrolytes used in the Daniel Cell are copper(II) sulphate and zinc sulphate, whereas the electrolytes used in the Galvanic Cell are the salts of metals of each Electrode.

Conclusion

An electrochemical cell is a device that uses a chemical reaction to generate electricity. A device that transforms chemical energy into electrical energy is known as a chemical energy converter. An electrochemical cell can only function if there is a chemical reaction that involves the exchange of electrons. Redox reactions are the name for these types of reactions. The voltage of a cell is what distinguishes it. Regardless of cell size, a certain type of cell generates the same voltage. If the cell is operated under ideal conditions, the chemical composition of the cell is determined by the cell voltage.