Resistors:

Some substances, like carbon, conduct electricity pretty well but not very well. The conductivity can be modified by adding impurities like clay to a carbon paste. Electrical components made in this manner are termed as resistors. They are significant in electronic circuits since they permit for the control of current flow. The best a resistor conducts, the lower is its resistance; the inferior it conducts, the higher is the resistance.

Electrical resistance is measured in ohms, sometimes represented by the uppercase Greek letter omega (?). We will sometimes use the symbol ? and sometimes spell out the word ohm or ohms, so that you will get used to both expressions. The higher the value in ohms, the higher is the resistance, and the more complicated it is for current to flow. In an electrical system, it is generally desirable to have as low a resistance, or ohmic value, as possible since resistance transforms electrical energy into heat. This heat is termed as resistance loss and in most cases symbolizes energy wasted. Thick wires and high voltages decrease the resistance loss in long-distance electrical lines. This is why gigantic towers, with hazardous voltages, are used in large utility systems.