What is Conduction in Science? — Definition & Examples
Conduction definition
Conduction is the thermal or electrical energy transfer through matter by direct contact between atoms or particles. The matter itself does not move, but thermal or electrical energy is conducted through the material.
Conduction only occurs in two ways: thermal conduction (heat transfer) and electrical conduction (electricity).
To better understand conduction, an understanding of several related terms is helpful:
Conductor – Any object that transfers thermal or electrical energy, or both, efficiently
Electrical energy – The kinetic energy caused by the movement of electrons in a substance; the faster these electrons move, the greater the electrical energy
Electricity – In purely scientific terms, this is a synonym for electrical energy, but it is generally associated with human-generated electrical energy, as from power plants
Heat – The transfer of thermal energy between two elements with a temperature difference; from a higher temperature material to a lower temperature material (this is the second law of thermodynamics)
Insulator – Any object that transfers thermal or electrical energy, or both, poorly. Insulators are poor conductors.
Temperature – The average kinetic energy of all the molecules in a substance; this measurement is not dependent on mass
Thermal energy – The total kinetic energy of a substance due to the movement of its atoms or molecules; the thermal energy of an object depends on its mass and temperature.
How does conduction work?
Thermal or electrical energy is transferred by direct contact between atoms or particles through conductors. Conductors efficiently transfer energy; insulators transfer energy poorly.
Conduction occurs in the common states of matter (solid, liquid, gas, plasma) but with varying degrees of efficiency.
In the diagram below, you can see thermal conductivity at work. Notice the heat flow from one material to the other.
When the two materials reach thermal equilibrium, where both materials are at the same temperature, conduction no longer occurs between the two materials.
Heat transfer definition
Heat is the term given to the transfer of thermal energy from a material or region of high thermal energy to a material or region of low thermal energy. Conduction of heat is also called heat transfer.
All materials can conduct thermal energy to some degree, though some are far more efficient than others.
Thermal conduction can occur in all four common states of matter, with solids being the most efficient, followed by plasmas, liquids, and gases. A typical hot plasma is about as thermally conductive as copper.
Good conductors of heat
Metals, for example, have good conductivity of heat. They generally move heat efficiently and are good heat conductors. Fabrics and wood tend to provide poor heat conduction.
The materials with the greatest thermal conduction are:
Zinc
Graphite
Tungsten
Aluminum
Beryllium oxide
Silicon carbide
Gold
Copper (and hot plasma)
Silver
Diamond
Though diamond is the best thermal conductor, its high cost makes it impractical for everyday use to conduct heat. The same is true of the high cost of silver and gold, which is why copper cookware is both popular and costly.
Electrical conduction
Generally, if a substance is a good thermal energy conductor, it will also be a good electrical conductor. This is not always true; mica, for example, is a heat conductor but an electrical insulator.
Saltwater is a poor heat conductor but a good electrical conductor.
Still, in general, the same close packing of atoms and relatively free movement of their electrons that makes thermal energy move about in the substance also makes the electrons’ electrical energy move about.
Good conductors of electricity
The materials with the greatest electrical conduction are:
Nickel
Cobalt
Zinc
Tungsten
Calcium
Aluminum
Gold
Copper
Hot plasma
Silver
Other materials can conduct electricity even if they are not great or even good conductors of thermal energy.
Water straight from your faucet is very difficult and expensive to heat, but water is a good electrical conductor. Electric current flows more easily the more dissolved minerals the water has in it.
Pure water, with no dissolved solids, is not electrically conductive, however.
Air, a mixture of gases, is generally not a good conductor of either heat or electricity.
Air, like water, is considered an insulator. Yet when the particles in air receive a strong electrical charge from, say, built-up static (from an electrical field when lightning is about to strike or from a power line’s electrical field), the air can conduct electricity.
Conduction examples
You have probably had the unfortunate accident of touching the handle of a metal spoon that was sitting in a hot liquid, like coffee, tea, cocoa, or soup on your stove. Though the handle is not in the liquid, it still got hot. This is the conduction of heat.
The metal particles in the spoon gained energy from the hot liquid and transferred, or conducted, that energy up to the metal spoon particles far above the liquid. Then, that heat energy is transferred into your hand, causing a burn. Ouch!
Unfortunately, the same energy conduction can happen with electrical energy by touching a bare wire or sticking a fork into an electrical socket. That transfer of electrical energy into you can cause much worse than a bad burn; that conduction can be fatal!
Fortunately, most homes have circuit breakers or fuses to prevent severe electrical shock, but the conduction of electricity is nothing to play with. Respect the power and danger of conduction.
Conduction quiz
Check your understanding of conductors by tackling these questions.
In your own words, what is a conductor?
How would you define thermal energy?
What is the transfer of thermal energy called?
Are all good heat conductors also good electrical conductors?
What can plasmas do that gases cannot?
Please give yourself the chance to shine before you look at our answers below.
In your own words, you might have said that a conductor is a substance that efficiently transfers thermal or electrical energy (or both) from atom to atom or from molecule to molecule within the substance.
You might define thermal energy as the total kinetic energy of the particles in a given substance; this means thermal energy depends on both the mass and temperature of the substance.
The transfer of thermal energy is called heat.
Not all good heat conductors are also good electrical conductors, as with mica, but in general, they are.
Plasmas can conduct electricity very well, which gases cannot do.