Resistor

                                          Resistor 

        Resistors ate the most fundamental and commonly used of all electronic components, to the point where they are almost taken for granted. There are many different types of resistor available for the electronics constructor to choose from, very small surface mount chip resistors up to large power resistors.

        The principal job of a resistor within an electrical or electronic circuit is to "resist"(hence the name RESISTOR), regulate or to set the flow of electrons (current) through them by using the type of conductive material from which they are composed. Resistors can also be connected together in various series and parallel combinations to form resistor networks which can act as voltage droppers.voltage dividers or current limiters within a circuit.

         Resistors are what are called "Passive Devices", that is they contain no source of power or amplification but only attenuate or reduce the voltage or current signal passing through them. This attenuation results in electrical  energy being lost in the form of heat as the resistor resists the flow of electrons through it.

         Then a potential difference is required between the two terminals of a resistor for current to flow. This potential difference balances out the energy lost. When used in DC circuits the potential difference , also known as a resistors voltage drop, is measured across the terminals as the circuit current flows through the resistor.