Electricity Project

1. RESISTANCE AND RESISTIVITY
AFROZ HUSSAIN SHAIK
R.No. 25, X-G,
AECS-4

2. RESISTANCE
 Resistance is a property of conductor due to which it resists
the flow of electric current through it.
 It is the ratio of the potential difference to current i.e. R = V/I
 Its SI unit is Volts/Ampere or Ohms ( denoted as Ω )
 Reciprocal of resistance is called Conductance (C). SI unit is
Ohm-1 i.e. Ω-1
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3. FACTORS AFFECTING RESISTANCE
1. R is proportional to resistivity, R α ρ
2. R proportional to length of conductor, R α l
3. R is inversely proportional to cross section area of the
conductor, R α (1/A)
 Therefore, from (1), (2) and (3)
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A
l
R



4. SPECIFIC RESISTANCE/ RESISTIVITY
 Specific resistance is the resistance of the conductor unit length
and unit cross sectional area i.e.
if l = 1m and A = 1m2 then R = ρ
 It depends on material of the conductor at given temperature
 Denoted by rho i.e. ρ
 SI unit is Ohm-m (Ω-m)
 ρ α Temperature of the conductor
 Also known as Resistivity
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l
RA



5.  Temperature increases resistivity increases
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6. RESISTIVITY TABLE OF DIFFERENT MATERIALS
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7. TYPES OF RESISTANCES
 Fixed Resistance : Their value does not change under constant
physical conditions. They are set at a physical value.
 Variable Resistance : Their resistance can be easily changed by
changing area of cross section and length.
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8. THANK YOU
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