Page 23 - CHAPTER-1 (Electricity)

CHAPTER 1

ELECTRICITY

F. Factors on which the Resistance of a Conductor

depends

Length of the conductor

• Resistance (R) is directly proportional to length(l) R∝l

• When length is doubled/halved, resistance is also doubled/halved.

Area of cross section of the conductor

• Resistance (R) is inversely proportional to area of cross section (A)

1
R∝
A

• When area of cross section is doubled, resistance is halved.

• When area of cross section is halved, resistance is doubled.

Nature of the material of the conductor

• Resistance depends on nature of the material.

• Some materials have low resistance and some have high resistance.

l l
R∝ or R=ρ
A A

where, is the constant proportionality and is called resitivity or

specific resistance of the conductor.

Mental floss!

Post stretching if length increases by n times then resistance will

increase by n times i.e. R =n R . Similarly if the radius is reduced
2
2
1
2
1
1
by times then area of cross-section decreases times so the
n n 2
4
4
resistance becomes n times i.e. R =n R .
1
2

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