Question

The colour code of carbon resistor is brown is, Brown, Black and Red. The value of the resistor is?
A) \[10\Omega \pm 5\% \]
B) \[1k\Omega \pm 2\% \]
C) \[100\Omega \pm 2\% \]
D) \[10\Omega \pm 2\% \]

Answer 1

Hint: Carbon resistor is one of the most common compact-sized types of electronic passive device. Carbon resistances are made from solid cylindrical resistive elements with embedded wire leads or metal end caps. Due to the compact size of carbon resistors color coding helps to quickly identify its resistive value and the percentage of tolerance of the carbon resistors.

Complete answer:
Carbon resistors are commercially used passive devices because they offer a very high resistance with a very compact size. The colors are used for the coding of carbon resistors mainly because in the small electronic circuit it is very difficult to calibrate the resistance of the tiny bunch of carbon resistors so for our sake of simplicity we are using colors in the coding purpose.
  Coding of colors
1. Brown = 1(Magnitude/Significant Number)
2. Black = 0(Magnitude/Significant Number)
3. Brown = 10(Multiplier)
4. Red = ±2%(Tolerance)
So we get the required value for resistance as:
\[R = (10 \times 10)\Omega \pm 2\% \]
\[ \Rightarrow R = 100\Omega \pm 2\% \]

Hence, option (C) is the correct answer.

Note: In order to tackle these kinds of questions from the topic of color-coded carbon resistors we have to remember the different values for the codes for different bands on the carbon resistor. For the sake of simplicity, one should learn the mnemonics for coding as – B B R O Y of Great Britain has a Very Good Wife.

Colors	Magnitude	Multiplier	Tolerance(%)
Black	0	\[{10^0}\]	Gold - \[ \pm 5\]
Brown	1	\[{10^1}\]	Silver- \[ \pm 10\]
Red	2	\[{10^2}\]	No color- \[ \pm 20\]
Orange	3	\[{10^3}\]
Yellow	4	\[{10^4}\]
Green	5	\[{10^5}\]
Blue	6	\[{10^6}\]
Violet	7	\[{10^7}\]
Grey	8	\[{10^8}\]
White	9	\[{10^9}\]

Tolerance in the carbon coded resistor indicates up to how much percentage the original value of resistance will differ. We can also call it a percentage error in the resistance. One should also note that the value of tolerance percentage in the carbon resistor also varies with colors that are other than Gold, Silver, and No color. For example, for red, the tolerance percentage will be ± 2%.