Resistance

A resistor is part of a circuit that resists the flow of electrical current. It is the load in a circuit and converts the electrical energy to another form of energy. The unit of measurement for resistance is the ohm portrayed by the green letter for omega.

The amount of resistance offered by the resistor is determined by what it is made of, the size of the resistor, and the temperature. The resistance increases with length and decreases with diameter.

Ohm's law was determined in 1827 by Georg Simon Ohm. He discovered that the ratio of voltage to current was constant to a given conductor. The relationship can be written as an equation (above). R is resistance (in ohms). V is voltage. I is the current. All conductors resist electricity to a certain extent. Not all of them, however, obey Ohm's law. The resistance of a material depends on its temperature, and resistance increases with temperature. The law forms the basis for the definition of resistance, but it is not technically a law because it does not apply in all circumstances.