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Conductor and Insulators Physics Important Notes for Class 12

Conductor and Insulators Physics Notes for Class 12, 12th physics, class 12 physics

Conductor and Insulators Physics Notes for Class 12

Physics Notes for Class 12 :- The conductor is a material that allows charge to pass through it freely whereas insulators are the materials that block the current to pass through them. Some examples of conductors are aluminum, nickel, tin, lead, keys, etc whereas some examples of the insulator are plastic, rubber, wood, etc. There are materials which come between conductors and insulators are known as a semiconductor, has the conductivity more than the insulator but less than the conductor either this is due to doping or by the effect of temperature.


Conductors are the device having a conductivity greater than 103 s/cm. Basically, electrical properties of any material depend on electronic population inside an atom as conduction is the result of the motion of electrons within the bands. In case of conductors, the conduction band is almost full and conduction band overlaps with valence band hence there us full conduction or full flow of electron from one band to another. Even at low temperature, it results in higher conductivity.

Conductor and Insulators Physics Notes for Class 12, 12th physics, NCERT physics

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Semiconductors have conductivity for silicon (it can range from 10-5S/cm to 103S/cm). Their conduction is almost empty and valence band is almost full, the energy gap between the conduction band and valence band is around 1eV. Their no such elements like semiconductors occurs naturally they are formed by doping in insulators. At the high temperature, they start conducting.

Conductor and Insulators Physics Notes for Class 12, 12th physics, NCERT physics class 12


In case of insulators, the conduction band is empty and there is a huge gap between the conduction band and valence is around 9eV and the conductivity is less than 10 -8 s/cm which means no conductivity.

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Conductor and Insulators Physics Notes for Class 12, 12th physics, NCERT physics class 12

Terms related to the topic:

  • Energy band:

They consist of a large number of energy levels closely placed inside a crystalline material. These energy levels split and form two continuous bands known as the conduction band CB and the valence band VB, two continuous energy bands exist (CB and VB), separated by a forbidden band, which is not accessible for electrons

  • Conductivity:

Electrical conductivity is the measure of the amount of electrical current a material can carry or it’s ability to carry a current. Electrical conductivity is also known as specific is an intrinsic property of a material. Electrical conductivity is denoted by the symbol σ and has SI units of siemens per meter (S/m). In electrical engineering, the Greek letter κ is used.

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