Asked in Electronics EngineeringEnergyElectrical Engineering
How do you convert electrical energy into heat energy?
May 05, 2013 11:27AM
Whenever electrical current encounters resistance, heat is generated.
Many home heating appliances (e.g. toasters, water heaters) work on this principle as well as tools (e.g. soldering iron, hair dryer) and even industrial furnaces. In each case, the resistance doing the heating has its specific performance characteristics that is has to meet, but the underlying scientific principle is the same.
The simplest electronic component is probably the resistor.
A resistor has no purpose other than to "resist" the flow of electricity. It performs no function other than turning electrical energy into heat energy. (Often the purpose is not to generate heat, but to control voltage or current and the generation of heat is secondary.)
If a current I flows through a resistor R, then the rate of power, P, is
Similarly, if a voltage drop of V occurs across a resistor, the Power is,
These equations are the same as saying that power associated with a resistor is, P=VI.
The power is the rate at which heat is generated and therefore the rate at which electrical energy is converted to heat energy.
Heat is no longer thought of as 'thermal energy' or as 'heat energy' but, rather, as energy in transit between a warmer body and a cooler body. If you like, it's thought of as being a 'process' or a 'transition', rather in the same way 'rain' describes water as it changes from being a vapour (a cloud) to a puddle! What used to be though of as 'heat energy' or 'thermal energy', these days, is called internal energy and describes the sum total of all the various types of energy within a body.
Work is thought of in a similar way to heat, except that it describes energy in transit from one form into another. For example, a motor does work when it converts electrical energy into kinetic energy.
So, when a current passes through a conductor, work is done on that conductor, meaning that the electrical energy is converted into internal energy, causing the conductor's existing internal energy to rise. This is accompanied by a temperature rise and, because the conductor's temperature is now higher than its surroundings, heat transfer takes place from the warmer conductor to the cooler surroundings.
So the process of converting electrical energy into heat is: electrical energy becomes internal energy (work is done), causing the internal energy of the conductor to rise; this is accompanied by a rise in the conductor's temperature, causing heat transfer to take place from the conductor to its surroundings.