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12th Physics Electrical Resistance Online Notes | NCERT Solutions

12th physics Electrical Resistance Online Notes NCERT Solutions

12th Physics Electrical Resistance Online Notes and NCERT Solutions

12th Physics : We offer one of the finest 12th Physics course to our students so that they can easily score good marks in the board exams. Keeping in view the latest pattern of question paper of the CBSE board exams, our faculty has developed the Class 12 Physics notes, sample papers, and NCERT solutions accordingly. Join us today…!

In this article, ‘Electrostatic Resistance’ from Class 12th Physics is being discussed.

Electrical Resistance

Resistance: The hindrance offered by a conductor to the flow of current.SI unit of resistance is ohm.The Electrical Resistance of a conductor depends on its length‘l’,cross-sectional area ‘A’ and nature of material and is given by

R= ?l/A

where ? is the resistivity of the material of the conductor.


Colour code for carbon resistances: Very high resistances are made of carbon. The value of high resistance is specified by four bands of different colors.

The first three bands represent the value of resistance while the last band represents tolerance. The first band represents the first digit, the second band represents the second digit and thethird band represents multiplier in powers of 10. The color of the fourth band tells the tolerance.The absence of thefourth band means a tolerance of 20%.

The following table gives the color code:

12th physics Electrical Resistance Online Notes NCERT Solutions

For practice sets of Current Electricity & more, click on NCERT Physics Class 12.

To memorize the color codes, the following sentence is of great help:

12th physics Electrical Resistance Online Notes NCERT Solutions

Ques: Determine the resistance of a resistor with the following colors for the rings:

yellow, red, orange,gold.


Ans: We know numbers for yellow, red, orange, goldis 4,2,3 and 5% respectively.


R = 42×103Ω ±5%


QuesDetermine the resistance of the resistor in the following figure:

12th physics Electrical Resistance Online Notes NCERT Solutions
Ans: Using table,

Resistance R = 47×102Ω ±5%


Ques: How will you represent a resistance 3700 Ω±10% by color code?

Ans: The value of carbon resistance = 3700 Ω±10%

=37×102 Ω±10%

The color attached to numbers 3,7,2 are orange,violet and red respectively.

For 10% accuracy,the color is silver. Thus the bands of color on carbon resistance in the sequence are orange, violet, red and silver.


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