# Joule heating

Joule heating is the process by which the passage of an electric current through a conductor releases heat. It was first studied by James Prescott Joule in 1841. Joule immersed a length of wire in a fixed mass of water and measured the temperature rise due to a known current flowing through the wire for a 30 minute period. By varying the current and the length of the wire he deduced that the heat produced was proportional to the electrical resistance of the wire multiplied by the square of the current. This relationship is known as Joule's First Law. The SI unit of energy was subsequently named the joule and given the symbol J. The commonly known unit of power, the watt, is equivalent to one joule per second.

It is now known that Joule heating is caused by interactions between the moving particles that form the current (usually, but not always, electrons) and the atomic ions that make up the body of the conductor. Charged particles in an electric circuit are accelerated by an electric field but give up some of their kinetic energy each time they collide with an ion. The increase in the kinetic or vibrational energy of the ions manifests itself as heat and a rise in the temperature of the conductor. Hence energy is transferred from the electrical power supply to the conductor and any materials with which it is in thermal contact.

Joule heating is also referred to as ohmic heating or resistive heating because of its relationship to Ohm's Law. It forms the basis for the myriad of practical applications involving electric heating. However, in applications where heating is an unwanted by-product of current use (eg. load losses in electrical transformers) the diversion of energy is often referred to as resistive losses. The use of high voltages in electric power transmission systems is specifically designed to reduce such losses in cabling by operating with commensurately lower currents. The ring circuits, or ring mains, used in UK houses are another example, where power is delivered to outlets at lower currents, thus reducing Joule heating in the wires.
Electric current is the flow (movement) of electric charge. The SI unit of electric current is the ampere (A), which is equal to a flow of one coulomb of charge per second.

## Definition

The amount of electric current (measured in amperes) through some surface, e.g.
In science and engineering, conductors, such as copper or aluminum, are materials with atoms have loosely held valence electrons. See electrical conduction.

## Conductors in context

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James Prescott Joule

James Joule - English physicist
Born November 24 1818
Salford, Lancashire, England
18th century - 19th century - 20th century
1810s  1820s  1830s  - 1840s -  1850s  1860s  1870s
1838 1839 1840 - 1841 - 1842 1843 1844

:
Subjects:     Archaeology - Architecture -
Mass is a fundamental concept in physics, roughly corresponding to the intuitive idea of "how much matter there is in an object". Mass is a central concept of classical mechanics and related subjects, and there are several definitions of mass within the framework of relativistic
Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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Temperature is a physical property of a system that underlies the common notions of hot and cold; something that is hotter generally has the greater temperature. Temperature is one of the principal parameters of thermodynamics.
minute is a unit of time equal to 1/60th of an hour and to 60 seconds. (Some rare minutes have 59 or 61 seconds; see leap second.)

The minute is not a SI unit, however it is accepted for use with SI units. The correct abbreviation for minute or minutes is "min".
proportionality, see Proportionality (disambiguation).

In mathematics, two quantities are called proportional if they vary in such a way that one of the quantities is a constant multiple of the other, or equivalently if they have a constant ratio.
Electrical resistance is a measure of the degree to which an object opposes an electric current through it. The SI unit of electrical resistance is the ohm. Its reciprocal quantity is electrical conductance measured in siemens.
square of a number is that number multiplied by itself. To square a quantity is to multiply it by itself. Its notation is a superscripted "2"; a number x squared is written as x2.
Joule's laws are a pair of laws concerning the heat produced by a current and the energy dependence of an ideal gas to that of pressure, volume, and temperature, respectively.
International System of Units (abbreviated SI from the French Le SystÃ¨me international d'unitÃ©s) is the modern form of the metric system.
energy (from the Greek ενεργός, energos, "active, working")[1] is a scalar physical quantity that is a property of objects and systems of objects which is conserved by nature.
The joule (IPA: [dʒuːl] or [dʒaʊl]) (symbol: J) is the SI unit of energy.
WATT

Branding NewsTalk 1240
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A subatomic particle is an elementary or composite particle smaller than an atom. Particle physics and nuclear physics are concerned with the study of these particles, their interactions, and non-atomic matter composed from them.
Electron

Theoretical estimates of the electron density for the first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Composition: Elementary particle
Family: Fermion
Group: Lepton
Generation: First
atom (Greek ἄτομος or Ã¡tomos meaning "indivisible") is the smallest particle still characterizing a chemical element.
ion is an atom or molecule which has lost or gained one or more electrons, making it positively or negatively charged. A negatively charged ion, which has more electrons in its electron shells than it has protons in its nuclei, is known as an anion
Charge or Charged may refer to:
• Charge (physics), the susceptibility of a body to one of the fundamental forces
*electric charge
*color charge
*magnetic charge

electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources, and switches.
acceleration is defined as the rate of change of velocity, or, equivalently, as the second derivative of position. It is thus a vector quantity with dimension length/timeÂ². In SI units, acceleration is measured in metres/secondÂ² (mÂ·s-Â²).
electric field. This electric field exerts a force on other electrically charged objects. The concept of electric field was introduced by Michael Faraday.

The electric field is a vector field with SI units of newtons per coulomb (N C−1
kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its current velocity.