James Prescott Joule

In 1847, he married Amelia Grimes, daughter of Mr. John Grimes, Comptroller of Customs, Liverpool. They had two children, Benjamin Arthur and Alice Amelia.

In 1854 his wife and son passed away. After this unfortunate incident, he lived as a widower for the rest of his life working tirelessly.

The British government granted him two hundred pound sterling as pension for his lifetime work and achievements. His unparalleled study in the field of energy and its dimensions still forms the basis for many of the researches undertaken today. The S.I. unit of energy and work, Joule, is named after him.

He was born on 24 December, 1818 in Manchester, England to Benjamin Joule, a wealthy brewer and Alice Prescott Joule, daughter of John Prescott of Wigan. He was one of the five children of Benjamin & Alice.

He was a delicate and frail child, unable to attend regular school and received his early education at home from his aunt.

As a child, he was fascinated with electricity and its effects. He used to conducts experiments at home and in one of the experiments in one of experiments, he inadvertently shocked and knocked out one of his servants.

His father’s health declined and he, along with his elder brother, Benjamin, was forced to work in brewery, at the age of 15. Alongside, he received his education from John Dalton, a famous English chemist.

In 1838, at the age of nineteen, he constructed an electro-magnetic engine.

In 1840, he worked on replacing the brewery’s steam engines with newly invented electric motor for scientific and economic purposes. He wanted to enhance the machines in his brewery for achieving higher efficiency.

In 1841, he designed an experiment to establish the relation between current, resistance and heat in a conductor. This relationship is known as Joule’s first law.

In 1845, he reported about the paddle wheel experiment which helped him understand the concept of conservation of energy. He proposed that in the experiment, mechanical energy converted into heat energy and this later led to the ‘Law of Conservation of Energy’.

In 1847, he met William Thompson during one of his presentations at British Association in Oxford and collaborated with him to conduct several studies on thermal effects. They discovered the Joule-Thomson effect and absolute scale of temperature.

He studied the nature of heat, and discovered its relationship to mechanical work. This led to the law of conservation of energy, which led to the development of the first law of thermodynamics.

He gave Joule's first law which gives the relationship between the passage of electric current through a conductor and the amount of heat released. The law states - "the heat which is evolved by the proper action of any voltaic current is proportional to the square of the intensity of that current, multiplied by the resistance to conduction which it experiences."

His work with William Thompson led to the remarkable discovery known as the Joule-Thomson effect. It describes the temperature change of a gas or liquid when it is forced through a valve kept insulated so that no heat is exchanged with the environment.

He also worked on the absolute scale of temperature with William Thomson, also known as ‘Lord Kelvin’.