Other materials, like iron, offer more resistance. They are still conductors, but not as good as the others mentioned.
The size of the conductor, and its length are the other two things that affect its resistance. The smaller it is, the greater its resistance. Also, the longer it is, the greater its resistance. Therefore, when we only want to move electricity from place to place, we want relatively large, "good" conductors. Here, we do not want to make heat. In fact, we want to avoid it, because too much heat in the wrong place can cause a fire.
But when we want heat, we choose relatively small, "poor" conductors, and the more heat we want, the longer they must be. If you will think of the filament inside a lamp bulb; you may recall that it is a very fine wire, coiled so as to get a maximum length, and made of tungsten which has a high resistance.
Because of all these factors, this filament glows at a white heat, and is a source of both light and heat.
Make a Simple Resistance Heater
Materials you will need:
1 dry cell battery
1 foot iron picture wire
Pliers
Use a short strand of iron picture wire and hook the ends to the terminals of a dry cell battery. Use pliers so that you do not burn your fingers. Disconnect the wires as soon as they become hot. Tell why the wires heat.
