Created By : Rina Nayak

Reviewed By : Phani Ponnapalli

Last Updated : May 23, 2023

To Calculate Cell EMF one needs to have inputs details of anode and cathode. Provide potentials of cathode and anode details in respective input positions and then click on the calculate button so that it will process and provide Galvanic cell Electromotive Force (EMF).

Electropotential of anode[Eanode]
Electropotential of cathode[Ecathode]
Electromotive force of the galvanic cell[EMFcell]

EMF - Definition

The electromotive force is the voltage at the terminals of the source in the absence of an electric current. The concept of electromotive force refers to the amount of work required to separate the charge carriers in the source current, such that the force acting on the charges at the terminals of the source is not a direct consequence of the field. Emf is developed as a result of internal resistance.

EMF Formula

Electromotive force (EMF) is equal to the terminal potential difference when no current flows. EMF and terminal potential difference (V) are both measured in volts, however they are not the same thing. EMF (ϵ) is the amount of energy (E) provided by the battery to each coulomb of charge(Q) passing through.

EMF Equation is given by EMFcell = Ecathode - Eanode

  • EMF - electromotive force
  • Ecathode - Potential of the cathode
  • Eanode - Potential of the anode

Sources of EMF

Some sources of Electromagnetic force(EMF) are Transformers, Electrochemical cells, Thermoelectric devices, Solar cells, Electrical generators. The unit for electromotive force is Volt.

Types of Electrochemical Cell

Electrochemical cells convert chemical energy into electrical energy, Anode and cathode are fixed i.e anode is negative and cathode is positive. Remember this as a negative Diode (Anode).Passage of electrons from anode to cathode occurs. Anode undergoes oxidation, cathode undergoes reduction.

Galvanic Cell and Electrolytic Cell

A galvanic cell is a thing that has two metal bars connected by a wire. Electricity comes from one bar and moves across to the wire to the other bar. Cells that are able to generate electricity from the chemical reactions occurring in them are known as Voltaic cells or Galvanic cells.

Reduction and oxidation processes only occur together (it is not possible that these reactions will happen separately). That is why the redox reactions can be described as two half-reactions, one representing the oxidation process and one the reduction process. The cells which cause chemical reactions to occur in them once the electric current passes through them are known as electrolytic cells.

Electro Potential of Anode and Cathode

Nernst equation is Ecell = E°cell - (RT)/(nF) logQ.

Electrode E⁰ [V]
Li / Li⁺ -3.04
Ca / Ca²⁺ -2.86
Mg / Mg²⁺ -2.36
Al / Al³⁺ -1.69
Mn / Mn²⁺ -1.18
Zn / Zn²⁺ -0.76
Cr / Cr³⁺ -0.74
Fe / Fe²⁺ -0.44
Cd / Cd²⁺ -0.40
Co / Co²⁺ -0.28
Ni / Ni²⁺ -0.26
Sn / Sn²⁺ -0.14
Pb / Pb²⁺ -0.14
Fe / Fe³⁺ -0.04
H₂ / 2H⁺ 0.00
Bi / Bi³⁺ +0.32
Cu / Cu²⁺ +0.34
Ag / Ag⁺ +0.80
Hg / Hg²⁺ +0.85
Au / Au³⁺ +1.52

Cell EMF Examples

Question 1: Calculate the EMF of the cell for the reaction Mg(s)​+2Ag(aq)+​→Mg(aq)2+​+2Ag(s)​



EMg2+/Mg0​= −2.37V


[Mg2+]=0.001M; [Ag+]=0.0001M

E​o= EAg0​−EMg0​

Eo​= 0.80−(−2.37)= 3.17 V

E ​= Eo​ = −(0.0592/n)​ log ( [Mg2+]​/ [Ag+]2 )

E = 3.17−(0.0592/2) ​log (0.001​/ (0.0001)2)

E = 3.022 V

FAQs on Cell EMF

1. What is the symbol and units of EMF?

The electromotive force symbol is ε and Units of EMF are Volts.

2. What is the standard EMF of a cell?

The standard electromotive force of a cell is 1.100 v in an ideal solution.

3. What is EMF Equation?

EMF equation EMFcell = Ecathode- Eanode. The electromotive force of a galvanic cell can be calculated by subtracting the potential of the cathode from the potential of the anode.

4. What material can block EMF?

Materials used for electromagnetic shielding include sheet metal, metal screen, and metal foam. Sheet metals for shielding include copper, brass, nickel, silver, steel, and tin.

5. Why is Nernst equation used?

The Nernst Equation enables the determination of cell potential under non-standard conditions. It relates the measured cell potential to the reaction quotient and allows the accurate determination of equilibrium constants (including solubility constants).

6. What is meant by the Voltaic cell?

Cells that are able to generate electricity from the chemical reactions occurring in them are known as Voltaic cells.