Question

Red, orange, black are the colour bands on resistors. Find its resistance.
A. $23\text{ }\Omega \pm 20$
B. $25\text{ }\Omega \pm 10$
C. $32\text{ }\Omega \pm 20$
D. $53\text{ }\Omega \pm 15$

Answer 1

To solve this, we must remember the colour code of resistors. The first two colours signify the first two digits of the resistance and the third digit signifies a multiplier value.

Complete answer:
The first colour is red. This signifies the digit 2. The second colour is orange. This signifies the digit 3. Hence, the first two digits will be 23. The third colour is black This signifies the multiplier ${{10}^{0}}$ which is equal to 1. 23 is hence multiplied by 1 which will give us 23.

Therefore, option A, that is, $23\text{ }\Omega \pm 20$ gives us the resistance.
$25\text{ }\Omega \pm 10$ signifies red, green and black. $32\text{ }\Omega \pm 20$ signifies orange, red and back. $53\text{ }\Omega \pm 15$ signifies green, orange and black.

Note:
$20$ represents tolerance. Although tolerance is represented by fourth band in the resistor, a $20$ indicates no band at all. The percentage error in resistance is represented by the tolerance.
We can remember the colour coding of resistors by memorizing the following phrase:
“ B.B. Roy Of Great Britain Visited GateWay of India.”
Here, the first B stands for black, the second B stands for brown, R stands for red, O stands for orange, Y stands for yellow, G stands for green, B stands for blue, V stands for violet, G stands for grey and W stands for white. The numbering starts from 0. The first colour, that is black represents the digit 0 and multiplier ${{10}^{0}}$. Similarly, the second colour, that is brown represents the digit 1 and multiplier ${{10}^{1}}$ and so on.