Joule heating

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Joule heating

Joule heating, also known as ohmic heating and resistive heating, is the process by which the passage of an electric current

Electric current

Electric current is the flow of electric charge. The electric charge may be either electrons or ions.The International System of Units unit of electric current intensity is the ampere....
through a conductor releases heat

Heat

In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic system to another due to a difference in temperature....
. It was first studied by James Prescott Joule

James Prescott Joule

James Prescott Joule Fellow of the Royal Society was an English physicist and brewing , born in Salford, Lancashire. Joule studied the nature of heat, and discovered its relationship to mechanical work ....
in 1841. Joule immersed a length of wire in a fixed mass

Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
of water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
and measured the temperature

Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
rise due to a known current flowing through the wire for a 30 minute

Minute

A minute is a unit of measurement of time or of angle.The minute is a Unit of measurement of time equal to 1/60th of an hour or 60 seconds. In the Coordinated Universal Time time scale, a minute occasionally has 59 or 61 seconds; see leap second....
period. By varying the current and the length of the wire he deduced that the heat produced was proportional

Proportionality (mathematics)

In mathematics, two quantity 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....
to the electrical resistance

Electrical resistance

The electrical resistance of an object is a measure of its opposition to the passage of a steady electrical current. An object of uniform cross section will have a resistance proportional to its length and inversely proportional to its cross-sectional area, and proportional to the resistivity of the material....
of the wire multiplied by the square

Square (algebra)

In algebra, the square of a number is that number multiplication 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 x?....
of the current.

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Encyclopedia

Joule heating, also known as ohmic heating and resistive heating, is the process by which the passage of an electric current

Electric current

Heat

James Prescott Joule

Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
of water

Water

Temperature

Minute

Proportionality (mathematics)

Electrical resistance

Square (algebra)

Energy

In physics, energy is a scalar physical quantity that describes the amount of Work_ that can be performed by a force. Energy is an attribute of objects and systems that is subject to a conservation law....
was subsequently named the joule

Joule

The joule is the SI derived unit of energy in the International System of Units. It is defined as:One joule is the amount of energy required to perform the following actions:...
and given the symbol J. The commonly known unit of power, the watt

WATT

WATT is a radio station broadcasting a News radio-Talk radio-Sports radio format. Licensed to Cadillac, Michigan, it first began broadcasting in 1945....
, is equivalent to one joule per second.

It is now known that Joule heating is caused by interactions between the moving particles

Subatomic particle

A subatomic particle is an elementary particle or composite particle particle smaller than an atom. Particle physics and nuclear physics are concerned with the study of these particles, their interactions, and non-atomic QCD matter....
that form the current (usually, but not always, electrons) and the atom

Atom

|-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
ic ions that make up the body of the conductor. Charge

Charge

Charge or charged may refer to:...
d particles in an electric circuit are accelerated

Acceleration

File:Acceleration.JPGFile:Acceleration components.JPGIn physics, and more specifically kinematics, acceleration is the change in velocity over time....
by an electric field

Electric field

In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field ....
but give up some of their kinetic energy

Kinetic energy

The kinetic energy of an object is the extra energy which it possesses due to its motion. It is defined as the mechanical work needed to accelerate a body of a given mass from rest to its current velocity....
each time they collide with an ion. The increase in the kinetic or vibration

Vibration

Vibration refers to mechanical oscillations about an equilibrium point. The oscillations may be periodic function such as the motion of a pendulum or random such as the movement of a tire on a gravel road....
al 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

Power supply

Power supply is a reference to a source of electrical power. A device or system that supplies electrical or other types of energy to an output External electric load or group of loads is called a power supply unit or PSU....
to the conductor and any materials with which it is in thermal contact

Thermal contact conductance

In physics, thermal contact conductance is the study of heat conduction between solid bodies in contact. The thermal contact conductance coefficient, , is a property indicating the thermal conductivity, or ability to conduct heat, between two bodies in contact....
.

Joule heating is referred to as ohmic heating or resistive heating because of its relationship to Ohm's Law

Ohm's law

Ohm's law applies to electrical circuits; it states that the electric current through a conductor between two points is directly Proportionality to the potential difference or voltage across the two points, and inversely proportional to the Electrical resistance between them....
. It forms the basis for the myriad of practical applications involving electric heating

Electric heating

Electric heating is any process in which electrical energy is converted to heat. Common applications include heating of buildings, cooking, and industrial processes....
. However, in applications where heating is an unwanted by-product

By-product

A by-product is a secondary or incidental product deriving from a manufacturing process, a chemical reaction or a biochemical pathway, and is not the primary product or service being produced....
of current use (e.g., load losses in electrical transformers) the diversion of energy is often referred to as resistive losses. The use of high voltage

High voltage

The term high voltage characterizes electrical circuits, in which the voltage used is the cause of particular safety concerns and insulation requirements....
s in electric power transmission

Electric power transmission

Electric power transmission is the bulk transfer of electrical power , a process in the delivery of electricity to consumers. A power transmission grid typically connects power plants to multiple Electrical substation near a populated area....
systems is specifically designed to reduce such losses in cabling by operating with commensurately lower currents. The ring circuit

Ring circuit

In electricity supply, a ring final circuit or ring circuit is an electrical wiring technique developed and primarily used in the United Kingdom that provides two independent conductors for live, neutral and protective earth within a building for each connected load or socket....
s, or ring mains, used in homes are another example, where power is delivered to outlets at lower currents, thus reducing Joule heating in the wires.

Joule heating

See also