Explain colour code for carbon resistors giving examples.

Explanation

A colour code is used to indicate the value of the resistance of a resistor and its percentage relibility.
A carbon resistor has usually four bands A, B, C and D of different colours on its body. These coloured bands can be converted into a number by using standard colour codes.
The sequence of these colours can be remembered with the help of a sentence :
B B ROY of Great Britain has a Very Good Wife.
The bold face letters in the above sentence correspond to the colours Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Grey and White respectively. The colour of first two bands A and B corresponds of figures 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and the colour of the third band corresponds to multipliers `10^(1), 10^(2), 10^(3), 10^(4), 10^(5), 10^(6), 10^(7), 10^(8) and 10^(9)` respectively. If the colour of the fourth band is gold, the tolerance is 5%, in case the colour is silver, the tolerance is 10%. In case there is no fourth band, then its tolerance is 20%. (See table)

For example, let there be a resistor whose bands have the colours as indicated in fig. below. Here B and A is yellow, `:.` first significant digit is 4
B and B is violet `:.` second significant digit is 7 and band C is orange, then multiplier is `10^3`
Tolerance band D is gold,`:.` tolerance is `pm+ 5% `
Hence, resistance of given resistor is `(47 xx 10^(3)pm 5%)`