Question

What is the resistance of a carbon resistance which has bands of colour brown, black and brown?
A. \[1\,\Omega \]
B. \[10\,\Omega \]
C. \[100\,\Omega \]
D. \[1000\,\Omega \]

Answer 1

Hint:The first colour is the first digit of the resistance, the second colour is the second digit of the resistance. Then we multiply the formed two digit number with the value represented by the third colour as an exponent of 10.

Complete step by step solution:
When the body of the resistor is large enough to print the letters or number on it then the value of resistance, power rating and tolerance of a resistor are generally printed over the body of the resistor as numbers or letters.

But when the resistor is small then these ratings and information about the resistors is practically not possible to print on the resistor which can be read by the user. In case of small resistors like carbon resistors the values are coded with colour combination.

By knowing the value represented by the colour on the resistor, the resistance and tolerance can be evaluated. For the given carbon resistance, the band of colours are in order as brown, black and brown.
The value of brown colour is 1.
The value of black colour is 0
The first colour of the band is the first digit of the resistance value, the second colour of the band is the second digit of the resistance value and the third colour of the band is multiplier.

The colour order is as, Brown, Black, Brown.
So, the resistance of the given carbon resistor is,
$R= 10\times 10\,\Omega$
\[\therefore R = 100\,\Omega \]
Hence, the value of the resistance of the given carbon resistor is 100 ohm.

Therefore, the correct option is C.

Note: If we have given 4 colours in the band then the fourth colour represents the tolerance of the resistor. As in the given question the fourth colour is not given so the final value of the resistor is without tolerance value.