What Is a Joule

This is a unit of energy as described by the International System of Units named after an English physicist James Prescott Joule, it measures mechanical work, heat and electricity.

Illustrative description of a joule

It is simply described as:

Electrical energy unit that equals to work done by passing one ampere current through a one ohm resistance for one second.

Or an energy unit that equals work did by exerting a force of one Newton for one meter. Where a Newton is an SI unit of force that is the net amount of force required to move an object weighing one kilogram at the speed of one meter per second squared.

It is also described as the work done when one Newton is applied making the object move for one meter in the direction of the force. One joule equals 0.2388 calorie.

Another description of joule compares the work done using a steady current, coulombs and electromotive force. It says that the work achieved by the steady current will be equal to a product of the electromotive force in volts and the number of coulombs of the charge.

A joule refers to the amount of heat energy required to raise the heat measurement of a gram of water by one degree from fourteen and a half to fifteen and a half degrees centigrade.

Joule is usually a measure of potential energy, the energy stored within a substance or the heat energy in a given substance. It is a very small unit hence the use of kilo joule for scientific calculations and measurements. The flow of energy is measured in watts therefore one joule flowing per second is one watt, with this, one watt-hour will equal 3,600 joules.

Uses of joule

  • Chemists use the joule everyday to measure the energy changes in any chemical reactions. This helps calculate the strength of various atomic and chemical bonds necessary in chemical designs.
  • With the right knowledge of joules and properly designed chemical reactions, stable home products and pharmaceuticals can be engineered successfully.
  • The daily use of electricity is measured in watts that is here related to joules with one watt-hour equaling three thousand six hundred joules. Joules being the standard measuring units though is seldom mentioned in our electricity bills or electric appliances.
  • In nutrition, a joule is comparable to the calorie that is referred to as a measure of heat. A joule matches up to 0.2389 calories


The joule has a long history, many application and mathematical relations. However, basically it just refers to the measure of work done using various energy sources including mechanical, electrical and heat energy.  And since one joule is so small, the thousand multiple kilojoules is used scientifically.