September 22, 2008



You have found earlier that voltage is an electromotive force that forces the electrons to move from one point to another or from one circuit to another and the amount or the number of free electrons that are moving in a particular time is called current, another fundamental quantity in electronics that affects the behavior of electrons is the resistance.

Resistance is the property of any material that opposes or limits the flow of electrons. Letter “R” is used to denote resistance of a circuit. Ohm is the unit used to express the resistance of a circuit. One ohm is the resistance of a circuit or circuit element that permits a steady current flow of one ampere when one volt is applied to the circuit. The Greek letter “Ω” (omega) is used to represent ohm. The unit ohm is named after the famous scientist Georg Simon Ohm. Manufactured circuit parts containing definite amount of resistance are called resistors.