Electrical Fires – Why do electrical conductors, cables, wires generate heat?

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Electrical Fires – Why do electrical conductors, cables, wires generate heat?

In general every day life, we subconsciously accept and disregard the presence of electrical cables and wires, which proliferate around us.

We also neglect the naturally occurring circumstance that in use ‘all’ electrical conductors, cables, wires generate heat, yet what is the fundamental, physical phenomena that causes such heating?

The process by which the passage of an electric current through an electrical conductor produces heat, is referred to as Joule heating, or Ohmic heating or resistive heating.

Electric current is a flow fundamental atomic particles which possess electrical charge. In electric circuits this charge is often carried sub atomic particles called electrons.

An electrical conductor is an object or type of material that supports the flow of electrical current in one or more directions. Metals are good conductors of electrical current particularly copper, aluminium, silver and gold. Conversely an electrical insulator is an object or type of material that restricts the flow of electrical current. Good insulators are glass, air, plastic, rubber, and wood.

Joule heating is a fundamental/natural phenomena, and was first revealed by James Prescott Joule in December 1840, when publishing an abstract in the Proceedings of the Royal Society.

Joule heating is caused by interactions between the flowing fundamental particles of electrical current (electrons) and the body of the conductor (atomic ions), but how?

Given, an electrical voltage difference between two points of a conductor, this creates an electric field that accelerates the electrons through the electric field, giving them motion/movement (kinetic energy).


The latter is analogous to, …

The gradient of a hill (voltage), and given a gravitational field, which is a difference in mass between our planet earth, and say a ball, car or whatever at the top of the hill, on release such will roll and accelerate down the hill (kinetic energy) (electron flow).

When the electrons collide with atomic ions in the conductor, the electrons are scattered; their direction of motion becomes random rather than aligned with the electric field, which constitutes thermal motion (Heat). Thus, energy from the electrical field is converted into thermal energy.

The latter is analogous and obvious, i.e. a ball rolling down a hill hits a stone, rock, hole or whatever and its direction of motion is randomly changed. As the ball rolls down the hill and at the instant of impact the ball forfeits some of its kinetic energy, which is converted to work!

So regardless of what we do, electrical conductors, cables, wires will generate heat (energy), yet we as engineers, designers or individuals can control the generation of heating by providing a suitable method/vehicle to transfer the heat energy from the electrical conductor to another physical system, i.e. if we allow air to freely circulate around an electrical conductor, heat generation will be controlled, conductor temperature will stabilise, since heat will be dissipated from the conductor to the surrounding air.

However of we do not providing a suitable method/vehicle to transfer heat then logically conductor temperature will rise and in time fire ignition will ensue.


About Dr Robert Brown:

Eur Ing Dr Robert Brown (Robert) is the Executive Director of Fraser George and Associates Limited and is a Consultant and Forensic Engineer in the fields Electrical Electronic and Control Engineering.

Robert is an accomplished professional Electrical Expert Witness having prepared and presented many court compliant reports and presented oral evidence within the High Court, Crown Courts and County Courts.

Robert is a registered Chartered Electrical Engineer, specialising in the fields are control engineering, parameter data capture and accurate data ‘representation’. Robert graduated from Sheffield Hallam University with a first class honours degree in Electronic Systems and Control Engineering and followed this by completing doctorate research in Electrical Engineering, again at Sheffield Hallam University where Robert undertook research studies in the field of Disintegration and Arcing in Electrical Fuses. Robert is now considered to be a leading world expert in the field of electrical circuit protection systems, the phenomena of electrical fuse operation and the attributes of clearing ‘fault’ electrical current circumstances. Robert has published my pure and applied research studies in peer-refereed journals and at conference.

In his spare time Robert is a Formula 1 motor racing enthusiast and enjoys outdoor activities especially hill walking and scrambling, golf and fishing. Robert is a brass band enthusiast, a tuba player and band manager of Hatfield and Askern Colliery Band. When time allows Robert also enjoys travelling and reading any books associated with travel and popular science.


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For further information please contact Robert via;

Email,…robert.brown@frasergeorge.com   or   robertbrown@robertbrown.uk.com

Tel Land: +44 (0)1777 709175

Tel Mobile: +44 (0) 7976250624





Websites: www.frasergeorge.com and www.robertbrown.uk.com



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