NCERT 12th Class Physics Ohm’s Law and Resistance

NCERT 12th Class Physics Ohm’s Law and Resistance

Ohm’s Law

Ohm’s law:  It states that “the current flowing through a conductor is directly proportional to potential difference between the ends of the conductor provided physical conditions like temperature, pressure etc.  remain the same”.

i.e.   VαI

or V = IR

Here V is apotential difference,I is current and R is Resistance of the conductor.

Resistance: It is the ability of a conductor to oppose the flow of electric current.

SI unit of resistance is ohm.

Factors on which resistance of a conductor depends:

• Nature of the material of the conductor
• Length of the conductor ‘l’
• Area of cross-section ‘A’
• Temperature

ie R ∝l

R ∝ 1/A

R= 𝜌l/A

Where 𝜌 is resistivity of the material of the conductor.

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The resistivity of thematerial of a conductor:

𝜌=RA/l

If we have A=1m2 and l=1m

So 𝜌=R

The resistivity of the material of a conductor is defined as the resistance of the conductor having unit length and unit area of cross section. S.I. unit is ohm-meter  (Ω – m).

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Ohmic conductors: Ohmic conductors are the conductors which obey ohms law and for which V-I graph is linear.Eg: Metallic conductor.

Click for V-I graph

Click on Physics notes Class 12 for notes on various chapters and NCERT Solutions.

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