Why do electricity cable heat up?

In another blog about insulation in a loft, comment was made about electricity cable heating up. Why? What causes that?

Electricity is a movement of electrons. Atoms and molecules (more than 1 atom) have electrons orbiting a nucleus of Protons and Neutrons (Apart from Hydrogen - it only has a Proton, no Neutron).

Radiation is electrical and magnetic movement. The term electromagnetic radiation is used. Neither electricity or magnetism have any substance. They occur, and we can see the results, but not the form.

If bar magnets have a positive end and a negative end it is easy to move one magnet without actually touching the next one. Try positive to positive and the magnets will repel each other. Then a positive to a negative and they attract each other.

If you could rotate the magnet extremely fast between the two poles then the other magnet would also react. That is basically what is happening with an electric pulse.

Electricity can be generated using exactly that method. The result is AC (Alternating Current). Depending upon how many changes of polarity occur per second will determine how many pulses occur. The mains supply in the UK has 50, termed Hertz. Named after Heinrich Hertz, a German physicist (1857 – 1894).

When energy is applied to atoms or molecules the electrons will increase in speed. The consequence is more impacts / collisions. In substances that are fluid (gases and liquids), the atoms and molecules will bounce off each other going in different directions. An electron or two may break off and become free to join another atom or molecule. (that will be the subject of another blog).

In solid substances the atoms and molecules cannot freely move about. They can vibrate though. In doing so they collide with adjacent atoms and molecules causing them to vibrate. The energy travels via the vibrations.

As the electrons are whizzing around the nucleus at phenomenal speeds approaching that of the speed of light, the impacts are also massive. The speed of an object can be referred to as the velocity. An increase in velocity increases the impact force.

For an example: A bullet (projectile) dropped onto your foot is likely to bounce off without any damage. Put the same bullet in a gun and fire it at your foot and it is likely the projectile will go straight through your foot an out the other side. The difference being the velocity / speed.

The electrons are too small to see even with a microscope. However, the speed they travel at creates a massive impact. The do not form a bigger electron, they bounce off. The impact apart from causes a change of direction, also produces heat.

It is the collisions of billions of impacts that produce heat. When electricity is directed along a metal conductor such as a wire, the energy goes through all of the molecules like a Mexican Wave. If there is more energy that the wire can dicipate the heat, the wire become hotter.

In a similar way to say 100 people walking down a tunnel and there is enough space between them - no problem. However, if 1,000 people try going down the tunnel in the same amount of time they will produce more heat. The heat cannot discipate quickly enough. In a similar way to the wire. Make the cross section a larger diameter and the 1,000 people can easily go down the tunnel as ther is more space to disciate the heat. A larger diameter wire can transfer more current than a smaller diameter wire.

The electricity in the form of energy (electromagnetic) goes along the atoms and molecules at a tremendous speed.

More energy that the wire can handle will cause the wire to become hot. An electric bar coil heater (radiant), is an example of the wire becoming red hot. With a smaller diamenter wire and a different metal, it becomes a filament. The filament becomes white hot and produces light. In the air the filament would combust / burn out and break. In the 1800s Joseph Swan and Thomas Edison developed tha incadescent light bulb.

In the absence of oxygen the metal cannot combust.