RESISTOR COLOR CODE

A resistor is a two-terminal electrical component used in electronic circuits to oppose the flow of an electric current. If an object inserted in a circuit displays a current flow which is proportional to the voltage across it, the ratio of voltage V divided by current I will be constant. This constant ratio is called resistance R=V/I. It can be measured by a device called ohmmeter. In an ideal resistor R does not depend on the current. The Ohm's law states that I=V/R.



Since this is true only for materials that can be characterized by such a resistance, it sounds like a tautology. In reality the Ohm's law should be understood as the statement that there are substances [including solids and liquids], called electrical conductors, that display this kind of behavior, at least within certain range of currents. Physical resistors are characterized by their resistance, maximum power they can dissipate without failure, maximum working voltage, temperature coefficient, noise, and parasitic inductance. The SI unit of electrical resistance is the ohm, symbol Ω. Its reciprocal quantity is conductance measured in siemens. Electronic industry often uses a special coding system of colored stripes to indicate the component's value and tolerance (see resistor color chart). These markings were originally published by Electronic Industries Alliance as EIA-RS-279, and currently are specified by IEC 60062 Ed. 5.0. This graphical calculator works both ways- you can get resistances from color codes or generate the colour bands from ohm values (5%, 10% and 20% tolerance).


Note that only certain "standard" component values specified by Electronic Industries Association (EIA) and IEC publication 60063 may actually be available. See a complete Standard Decade Resistor Values table. Resistors may have different number of color bands depending on the tolerance. The same color scheme is used for capacitors (in picofarads pF) and inductors (in microhenries µH), although they usually have the numeric values actually stamped on them. Also see electrical formulas for the main circuit component connections in series and in parallel.