Cert 2- Resistors and Use in a circuit.

The color code used on resistors is:

0 Black 1 Brown 2 Red 3 Orange 4 Yellow 5 Green 6 Blue 7 Purple (Violet if your colour vision is very good) 8 Grey 9 White

The colour bands are read from left to right and the first band is close to one end of the body of the resistor.

Examples: [Red, Red, Red: 2 2 00 ohms or 2K2] [Yellow, Purple, Orange: 4 7 000 ohms or 47K] [Brown, Black, Brown: 1 0 0 ohms or 100R ] [Orange, Orange, Orange: 3 3 000 ohms or 33K] [Brown, Green, Red: 1 5 00 ohms or 1K5] [Brown, Green, Black: 1 5 no noughts, or 15 ohms] [Blue, Grey, Orange: 6 8 000 ohms or 68K] [Brown, Green, Green: 1 5 00000 ohms or 1,500,000 ohms or 1M5] [Yellow, Purple, Brown: 4 7 0 ohms ]

Fourth color on a resistor can also mean?

Gold: meaning "no zeros and divided by 10" and Silver: meaning "no zeros and divided by 100".

Each resistor has typically, three color bands to indicate its value. The first two bands are the numbers and the third band is the number of noughts:

Green: 5 Blue: 6 Red: 2 noughts Value: 5,600 ohms or 5.6K Yellow: 4 Purple: 7 Green: 5 noughts Value: 4,700,000 ohms or 4.7M or 4M7

Ohm

It is defined as the resistance between two points of a conductor when a constant potential difference of 1 volt, applied to these points, produces in the conductor a current of 1 ampere, the conductor not being the seat of any electromotive force.

This extra band is used to indicate the manufacturing tolerance of the construction of the resistor. Resistor values are never exact and this rarely has any significant effect on their use in circuits. If some circuit needs very accurate resistor values in it, then buy several resistors of the same nominal value and use an ohm-meter to measure that actual value of each particular resistor and if none are perfect, then use two or more resistors to give the exact value wanted. The tolerance band has the following codes:

Silver is ± 10% (i.e. a 10K resistor of this type should be between 9K and 11K) Gold ± 5% (i.e. a 10K resistor of this type should be between 9.5K and 10.5K) Red ± 2% (i.e. a 10K resistor of this type should be between 9.8K and 10.2K) Brown ± 1% (i.e. a 10K resistor of this type should be between 9.9K and 10.1K) Green ± 0.5% (i.e. a 10K resistor of this type should be between 9.95K and 10.05K) Blue ± 0.25% (i.e. a 10K resistor of this type should be between 9.975K and 10.025K) Purple ± 0.1% (i.e. a 10K resistor of this type should be between 9.99K and 10.01K)