Question

A carbon resistor of $\left( {47 \pm 4.7} \right)k\Omega $ is to be marked with rings of different colours for its identification. The colour code sequence will be:
A. Yellow-Green-Violet-Gold
B. Violet-yellow-Orange-Silver
C. Green-Orange-Violet-Gold
D. Yellow-Violet-Orange-Silver

Answer 1

Hint: In order to indicate the resistance value of a carbon resistor and its percentage accuracy a colour code is used. These colours are in increasing order of multiplier power and number from black, brown, red, orange, yellow, green, blue, violet, grey, and white. This sequence can be used to determine the colour code sequence for the carbon resistor.

Complete step by step answer:
A carbon resistor in use needs to be chosen so that it satisfies the need of the circuit. To choose the right resistor based on its resistance, a colour code is used to indicate the resistance value and its percentage accuracy. The colour code used throughout the world is shown below:

colour	Letter to remember by	Number	Multiplier	Colour	Tolerance
Black	B	0	${10^0}$	Gold	5%
Brown	B	1	${10^1}$	Silver	10%
Red	R	2	${10^2}$	No fourth band	20%
Orange	O	3	${10^3}$
Yellow	Y	4	${10^4}$
Green	G	5	${10^5}$
Blue	B	6	${10^6}$
Violet	V	7	${10^7}$
Grey	G	8	${10^8}$
White	W	9	${10^9}$

The easiest way to remember these colours is to associate them with their first letter only and the number which represents its power. BB ROY of Great Britain had Very Good Wife is a phrase used to memorize the colour code representation. Here the capital letters represent the first letter of the colour.
System of marking colours:
a. The first colour band on the carbon resistor represents the first significant figure.
b. The second colour band on the carbon resistor indicates the second significant figure.
c. The third band indicates the power of ten with which the above two significant figures must be multiplied to get the resistance value in ohm.
d. The fourth band indicates the tolerance or possible variation in the percent of the indicated value.
Considering the above points we can easily see that for a resistance of $\left( {47 \pm 4.7} \right)k\Omega $. We need yellow as the first colour, followed by violet. And as the resistance is in kilo ohm the power would be 3, and the colour corresponding to it will be orange.
Now, a tolerance of $ \pm 4.7k\Omega $ means that the tolerance in percentage is:
$ \pm 4.7k\Omega = \pm \dfrac{{4.7}}{{47}} = \pm 10\% $
So, the last colour will be silver.
Therefore, the correct option is D, i.e., Yellow-Violet-Orange-Silver

Note: The carbon resistors are widely used in electronic circuits like radio receivers, amplifiers etc. These are highly used because of their advantages including they are quite cheap and compact, and can have a wide range of values.