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Current Eletricity L-3

The document explains Ohm's law, which states that the current through a conductor is directly proportional to the potential difference across it, with resistance as a constant. It details the factors affecting electrical resistance, including length, area, and temperature, and introduces the concept of resistivity. The document also provides formulas for calculating resistance and resistivity, emphasizing that resistivity is dependent on the material and temperature but not on the dimensions of the conductor.

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Purushottam IWS
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3 views18 pages

Current Eletricity L-3

The document explains Ohm's law, which states that the current through a conductor is directly proportional to the potential difference across it, with resistance as a constant. It details the factors affecting electrical resistance, including length, area, and temperature, and introduces the concept of resistivity. The document also provides formulas for calculating resistance and resistivity, emphasizing that resistivity is dependent on the material and temperature but not on the dimensions of the conductor.

Uploaded by

Purushottam IWS
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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Ohm's law

Electrical Resistance

Resistivity or Specific Resistance


Random Motion of Charges
Conductor

Key

Cell
Flow of Current
Ohm's law :
It states that the current passing through a
conductor is directly proportional to the
potential difference across its ends,
provided the temperature and other
physical conditions (mechanical strain
etc.), remain unchanged i.e.
Where R is a constant called resistance of the
conductor.
Experimental set up of Ohm's law
Voltmeter=V1 Key Rheostat

Ammeter=I1
Voltmeter
V A
Ammeter
e
Experimental set up of Ohm's law
Voltmeter=V2 Key Rheostat

Ammeter=I2
Voltmeter
V A
Ammeter
e
Experimental set up of Ohm's law
Voltmeter=V3 Key Rheostat

Ammeter=I3
Voltmeter
V A
Ammeter
e
Graph between the current and the potential difference

V3

Potential Difference
V2

V1

Current
I1 I2 I3
Electrical resistance
The property of a conductor due to which it
opposes the flow of current through it, is called
resistance

Resistance = Potential Difference /Current


R=V / I
Slope of Graph, tanq =V/I=R
Unit of Resistance

Ohm
Symbol:-Ω
Factor
affecting
Resistance

Length
L1 R L

Length L2
Area
A1 R 1/A
Area
A2
Where is
R L/A a constant known
as resistivity of
the material of
R = L/A the conductor.
specific resistance.
Dependency of resistance
on temperature

 On increase in temperature of conductor


the resistance will increase
Rt=Ro(1+αΔt)
α= Temperature Coefficient (in 0C)
Ro =Resistance at o 0C
Rt =Resistance at T 0C
Specific
Resistance

= RˣA/L
If L= 1 m and A = 1 metre sq. then

=R
The resistivity of a substance is
numerically equal to the resistance
of a rod
Unit of Resistivity

= Ωm2/m

= Ωm
Resistivity does not depend on
(i) length
(ii) Cross Section of the wire
It depends only on
(i) Nature of material
(ii) Increases with rise in temperature

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