Passive component with a known resistance.

The value of resistance is usually shown by a set of coloured bands on the body of the component.

The resistor shown above is coded Orange, Green, Blue with a silver tolerance band.

Using the following table the resistance may be calculated from the first three bands, Orange = 3, Green = 5 and the multiplier is Blue = 106 = 1000000.

The silver band indicates a tolerance of ±10%

Therefore, the resistance is

35x106±10% Ohms

ColourBand 1Band 2Band 3
Black00100 = 1
Brown10101 = 10
Red20102 = 100
Orange30103 = 1000
Yellow40104 = 10000
Green50105 = 100000
Blue60106 = 1000000
Violet70107 = 10000000
Grey80108 = 100000000
Tolerance Codes
Gold = ±5%
Silver = ±10%
None = ±20%

There are a number of different types of resistors designed for different applications.

Carbon Film
A carbon film deposited on a small ceramic cylinder.

Metal Film
A thin film or metal particle mixture is used to control the resistance.

Wire Wound
A length of resistance wire wound onto a tube. These are very accurate and able to carry large currents.
The power disipated by a resistor is given by Joule′s law:
W = power disipated [Watt]
I = current [Ampere]
R = resistance [Ohm]
V = potential difference across resistor [Volt]
Enter two values and the other values will be calculated.

See also: Completion Resistor, Electrical Resistance, Fixed Resistor, Light Dependent Resistor, Photocell, Resistance, Shunt Resistor, Swamping Resistor, Tapped Resistor, Thermistor, Variable Resistor.

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Subjects: Electronics

Weblinks: This resistor calculator is popular because it calculates values for 4, 5 and 6 band resistors. Sketch, simulate, and share schematics.