Question

The three colours in a carbon resistor are red, black and orange. If the fourth colour is absent, then the value of tolerance of the resistor is

• A. ±2000 Ω
• B. ±1000 Ω
• C. ±3000 Ω
• D. ±4000 Ω
• E. ±200 Ω

Answer 1

The Correct Option is D

The color code for resistors is as follows:
Red = 2
Black = 0
Orange = \( \times 10^3 \)
So, the resistor value is: \[ (2 \times 10 + 0) \times 10^3 = 20 \times 10^3 = 20000 \, \Omega \] Since the fourth color (which indicates the tolerance) is absent, we assume a tolerance of ±20% for carbon resistors. The tolerance is calculated as: \[ \text{Tolerance} = 20\% \times 20000 = 4000 \, \Omega \]

Thus, the correct answer is (D): \( \pm 4000 \, \Omega \).

Answer 2

The colour code for a carbon resistor uses 4 bands:  

1st Band (Red): 2
2nd Band (Black): 0
3rd Band (Orange - multiplier): \( 10^3 \)
So, the resistance value is:
\( R = 20 \times 10^3 = 20000\,\Omega = 20\,k\Omega \) 

4th Band (Tolerance):
Since the fourth band is absent, the tolerance is assumed to be: 
\( \pm 20\% \) 

Tolerance value = \( 20\% \) of \( 20000\,\Omega \) = \( 0.2 \times 20000 = 4000\,\Omega \) 

Final Answer: \( \boxed{\pm 4000\,\Omega} \)