Electrochemical cells are a type of electrical cell that uses chemical reactions to produce an electromotive force, which is a source of power. The electromotive force (EMF) of a galvanic cell is the measure of voltage generated by that cell. A single cell consists of one anode (+) and one cathode (-).

Electrochemical cells contain more than one electrode and electrolyte, but still have only one anode and one cathode. The potential difference between an anode and cathode is called the electromotive force (EMF) of that cell. All galvanic cells have a negative electrode called an anode and a positive electrode called a cathode.

EMF definition

EMF (electromotive force) is the driving force behind the flow of charge through a circuit. It is measured in volts (V) and represents the difference in voltage between two points in a circuit. For example, consider a battery that has one terminal connected to one end of an iron nail and the other terminal connected to the other end of it. With no outside interference, electrons will naturally move from low potential to high potential until all parts are at equilibrium with each other. This establishes an electric field around the nail, which translates into an EMF for its entire length:

  • Potential difference = Voltage difference between two points
  • Electromotive force (EMF) = Difference between potentials at two ends when there is no current flowing


Voltage is a measure of the potential difference between two points in an electrical circuit. If you have ever been shocked, you know that electricity can be dangerous. In fact, the voltage can kill if it is too high or if it passes through your body for too long.

Voltage is measured in volts (V). A volt is defined as the amount of electrostatic force required to move one unit of positive charge from one point to another within an electric field when both points are at the same potential (zero volts).


There are two types of electromotive forces, galvanic cells, and electrolytic cells. In a galvanic cell, electricity is produced by the spontaneous decomposition of an electrolyte (a substance that conducts electricity through electron transfer). For example, when copper sulfate is dissolved in water and then exposed to air (oxygen), electrons separate from the copper ions in the solution and move toward oxygen molecules to form neutral copper atoms. When this happens at multiple locations within a circuit, it generates electricity.

The term “electrolysis” refers specifically to the production of metals from their minerals or salts using electric current. In contrast with other types of fuel cells such as hydrogen-powered internal combustion engines or steam turbines which convert stored energy into mechanical movement for generators; these devices use chemical reactions between electrodes and solutions—called electrolytes—to generate electricity directly within them with no moving parts involved aside from pumps used for circulation purposes only (so there’s no friction loss).

A single cell

A single cell consists of one anode (+) and one cathode (-). The anode is the positive terminal or the terminal where oxidation takes place. The cathode is the negative terminal or the terminal where reduction takes place. The electrolyte permeates through this porous barrier between these two terminals in order to allow ions to move freely between them.

Electrochemical cell

When you think of an electrochemical cell, you probably envision a battery. But in reality, any system that creates an electrical potential between two electrodes is considered an electrochemical cell. For example, if you attach a copper wire to each end of a zinc strip and place them both in a solution containing salt water (electrolyte), this would be considered one type of electrochemical cell—the other electrode being the copper wire on which electrons are transferred from the zinc strip to create electricity.

In this case, there are two different types of reactions taking place: oxidation reactions at the cathode where water is being reduced and reduction reactions at the anode where hydrogen gas is produced by oxidizing hydrogen ions as they come into contact with oxygen atoms.


What is meant by an electromotive force?

Electromotive force (EMF) is equal to the terminal potential difference when no current flows.

What is EMF measured in?

EMF is measured in volts but is different than the terminal potential difference.

What is the difference between EMF and voltage?

EMF or electromotive force is the potential difference generated by one or more cells or a changing magnetic field in a solar cell, and voltage is the potential difference measured at any two points in the magnetic field.