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Resistor color codes are painted bands that help in identifying the value, function, wattage, and tolerance of resistors. This is an important topic from the Current Electricity concept of the CBSE Class 12 Physics Syllabus.
Resistor Color codes were first provided by the International Standard IEC 60062 in 1922. The codes consist of a set of individual colored rings or bands in spectral order and these represent a digit of the resistor value.
The color code markings are read from left to right one band at a time. The band with the highest tolerance width is oriented to the right side. Each color is associated with a digit in the color chart and the first digit is hence identified. This first digit is also representative of the resistance value.
Resistor Color Code Table
To calculate the resistor value, the ‘left-hand’ band closest to the connecting lead is red from left to right. It can be written as,
Digit, Digit, Multiplier = Color, Color x 10 color in Ohms (Ω)
Read More: NCERT Solutions Class 12 Physics Current Electricity
Important Questions on Resistor Color Codes
Q.1. What is the importance of color coding? (1 Mark)
A.1. Color coding in resistors help in the identification of the resistor values and function. The color codes also give information about tolerance percentage and the power rating of the resistor based on its size.
Q.2. What are the resistor color code types? (4 Marks)
A.2. The resistor color codes are classified into the following three types:
- 4-Band type- most common type containing two bands, one for resistance and the other for multiplier and one for tolerance.
- 5-Band type- The third significant digit in some resistors is used to show precision. The first three bands are indicative of the resistance values, the fourth refers to the multiplier, and the fifth gives the tolerance value.
- 6-band type- These have an additional band to indicate the reliability or the temperature coefficient of the resistor measured in ppm./K. The sixth band is usually of brown color. Hence, if the temperature change of 10℃ is shown, the resistance value can change by 0.1%.
Q.3. How is the resistor color code determined? (1 Mark)
A.3. The color code of a resistor is determined by holding the resistor with its gold or silver band to the right. The reading of the codes is always done from left to right by convention. The color codes are selected from the bands, the colors are read from left to right and the value of resistance based on the color code is displayed.
Q.4. Is turquoise used in the color coding of resistors? (1 Mark)
A.4. The color turquoise is not used in the color coding of the resistors. The color coding involves the following colors only: Black, brown, Red, Orange, Yellow, Green, Violet, Blue, Grey, and White. These are all read from left to right as per convention.
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Q.5. Yellow is denoted by which digit in the resistor color code? (4 Marks)
A.5. Here is the list of colors denoted by the different digits:
- Black = 0
- Brown = 1
- Red = 2
- Orange = 3
- Yellow = 4
- Green = 5
- Blue = 6
- Violet = 7
- Grey = 8
- White = 9.
Q.6. What is the resistance of a resistor with the following color sequence- Red, Green, Red, Gold? (2 Marks)
A.6. The first two colors are the resistance values and so Red and Green represent numbers 2 and 5 respectively. The third color indicates the multiplier factor of 102. The last band is for the tolerance level and for Gold, the value would be ±5%. The resistance of the given resistor would thus be, 2500 ± 5% Ω or 2.5 kΩ.
Q.7. Determine the color code for a 1000 Ω resistor. (1 Mark)
A.7. A 1000 Ω resistor will have a four-band color code. The sequence would be Brown, Black, Red, and Gold. The multiplying factor of 100 (Red) and tolerance of ±5% (Gold).
Q.8. What is the value of resistance for the resistor with the color code as green, blue, yellow, and silver? (3 Marks)
A.8. From the color code table of resistors,
green = 5
blue = 6
yellow = 4
Silver = ± 10%
Thus the resistor is 560,000 Ω or 560 kΩ with a tolerance ± 10%
Q.9. What is the value of resistance for the resistor with the color code as- orange, white, brown, and gold (3 Marks)
A.9. From the color code table of resistors,
orange = 3
white = 9
brown = 1
gold = ± 5%
Thus the resistor is 390 Ω with a tolerance ± 5%
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Q.10. Determine the color on the resistor body if the resistor value is 200 kΩ (ignoring the value of tolerance)? (3 Marks)
A.10. From the resistor color code table,
2 is red
0 is black
4 is yellow
So the color on the resistor would be Red, Black, and Yellow.
Q.11. Determine the color on the resistor body if the resistor value is 1.2 MΩ (ignoring the value of tolerance). (3 Marks)
A.11. From the resistor color code table,
1 is brown
2 is red
5 is green
So the color of the resistor is Brown, Red, and Green.
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