Question

The resistance of a carbon resistor is 4.7 kΩ ± 5% . The colour of the third band is

• A. red
• B. violet
• C. orange
• D. gold

Answer 1

The Correct Option is A

Step 1: Identify the given resistor value clearly:

The given resistor value is \(4.7\,k\Omega \pm 5\%\).

Step 2: Resistor color-coding rules:

A resistor with four color bands is read as:

• 1st band: First significant digit
• 2nd band: Second significant digit
• 3rd band: Multiplier (power of 10)
• 4th band: Tolerance

Step 3: Decode the given resistor value (4.7 kΩ):

\[ 4.7\,k\Omega = 4700\,\Omega \]

Expressed in standard form:

\[ 4700 = 47 \times 10^2 \]

Here:

• First digit = 4 (Yellow)
• Second digit = 7 (Violet)
• Multiplier = \(10^2\), thus exponent = 2. The color corresponding to '2' is Red.

Thus, the third band (multiplier) is Red.

Final Answer: Option (A) Red

Answer 2

1. Understand the Resistor Value:
The given resistance is \(R = 4.7 \, \text{k}\Omega \pm 5\%\). This can be written as \(R = 4.7 \times 10^3 \, \Omega \pm 5\%\). In standard form for a 4-band resistor, this is \(47 \times 10^2 \, \Omega \pm 5\%\).

2. Recall the Resistor Color Code Standard (4-Band):
 

• Band 1: First significant digit.
• Band 2: Second significant digit.
• Band 3: Multiplier (power of 10).
• Band 4: Tolerance.

3. Identify Digits, Multiplier, and Tolerance:
From the value \(47 \times 10^2 \, \Omega \pm 5\%\):

• First significant digit = 4
• Second significant digit = 7
• Multiplier = \(10^2\)
• Tolerance = \(\pm 5\%\)

 

4. Determine the Color for Each Band using the Standard Code:
 

Color	Digit	Multiplier	Tolerance
Black	0	\(10^0 = 1\)
Brown	1	\(10^1\)	±1%
Red	2	\(10^2\)	±2%
Orange	3	\(10^3\)
Yellow	4	\(10^4\)
Green	5	\(10^5\)	±0.5%
Blue	6	\(10^6\)	±0.25%
Violet	7	\(10^7\)	±0.1%
Grey	8	\(10^8\)	±0.05%
White	9	\(10^9\)
Gold		\(10^{-1}\)	±5%
Silver		\(10^{-2}\)	±10%

• Band 1 (Digit 4): Yellow
• Band 2 (Digit 7): Violet
• Band 3 (Multiplier \(10^2\)): Red
• Band 4 (Tolerance 5%): Gold

5. Answer the Question:
The question asks for the color of the third band, which represents the multiplier \(10^2\). The color corresponding to a multiplier of \(10^2\) is Red.

Answer: The colour of the third band is (A) red.