Question

Find the colour code of a carbon resistor having a resistance of $470\Omega$ and a tolerance of 5%.

Answer 1

Carbon resistors often have a set of 4 coloured bands that correspond to the value of the resistance of the resistor. Band 1 represents the first digit, band 2 represents the second digit, band 3 represents the multiplier or the number of zeroes in the resistance value and band 4 represents the tolerance of the resistance value. The tolerance is indicated by gold, silver or no colour representing a tolerance of 5%, 10% and 20% respectively.

Complete step by step answer.
Step 1: List the number represented by each colour.

Colour	Number
Black	0
Brown	1
Red	2
Orange	3
Yellow	4
Green	5
Blue	6
Violet	7
Grey	8
White	9
Gold	5%
Silver	10%
No colour	20%

Step 2: List the value of the given carbon resistor.
The value of the given carbon resistor is given to be $470\Omega$ . So band 1 has the colour which represents the number 4, band 2 has the colour which represents the number 7 and the colour of band 3 corresponds to the number of zeroes in the given resistance value and it is 1.

The tolerance of the resistor is given to be 5%. So the colour of band 4 corresponds to the colour which represents a tolerance of 5%.
Thus the colour code of the carbon resistor as matched with the above table is yellow (4), violet (7), brown (1) and gold (5%).

Note: A certain trick used to remember the number represented by each colour is to use the acronym B.B. The ROY of Great Britain has a Very Good Wife. Each capital letter of this mnemonic corresponds to the colour starting with that letter and represents the number from 0 to 9. The first B in the acronym corresponds to black and the next B corresponds to brown. Also, the first G corresponds to green and the next G corresponds to grey.