In ancient times, people thought that heat was a material just as air is. They called it "caloric". When something got warm, they said, caloric flowed into it. When something cooled off, caloric flowed out of it. It did not bother them that they could not see caloric. They could not see air either!
Now we know that heat is not a material. It does not take up space. It does not weigh anything. Instead, it is a form of energy. And when we say that heat is a form of energy, we mean that it can be used to do work.
What to Do
1. Make a simple resistance heater.
2. Make some popcorn by:
(a) conduction (b) convection (c) radiation
"Resistance" Makes Heat
There are at least four ways that electricity can make heat. The one that we'll cover here is resistance heating. (The others are: dielectric heating, where the lines of force of an electrostatic field pass through a non-conductive material and heat it; the heat pump, which is a refrigerator in reverse; and electronic heating, which uses high frequency waves similar to radio waves to create high speed movement of the molecules or tiny particles which rub together to make heat.)
Resistance heating occurs because every conductor of electricity opposes the flow of current through it. Some conductors resist more than others. When they do, a certain amount of warming takes place. The more resistance that is offered, the more heating there is.
Some materials, like silver, copper, and aluminum, offer little resistance. We say they are good conductors.