FACTORS AFFECTING RESISTANCE AND RESISTIVITY OF A CONDUCTOR



 Resistance of a conductor is it’s ability to oppose the flow of current through it. There are several factors affecting resistance of a conductor 

1. Effect of length on resistance of a conductor 

As the length(l) of a conductor increases resistance of that conductor also increases. Resistance is directly proportional to length
ie, r α l

2. Effect of area of cross-section on resistance of a conductor 

As area of cross-section(a) of a conductor increases the resistance of a conductor decreases. Resistance of a conductor is inversely proportional to the area of cross-section of a conductor.
ie, r α 1/a

3. Nature of material 

Resistance offered by different materials is different. So resistance will vary according to the material used.
eg. Copper wire and iron wire of same thickness and length shows different resistance value.

4. Effect of temperature on resistance

As the temperature increases,The resistance of a conductor also increases. Temperature is directly proportional to the resistance of a conductor.

RESISTIVITY

We know factors affecting resistance are Nature of material, temperature, Length of conductor(L)-As length of a conductor increases resistance of conductor also increases. Length is directly proportional to resistance.(Rα L) and Area of cross-section(A)- As area of cross-section increases resistance of conductor decreases. Area of cross-section is inversely proportional to resistance.(R α 1/A)

From above statements,

      R α L/A
      R = a constant × L/A (Constant is the resistivity of material (ρ))
      R = ρ L/A
      ρ = RA/L
SI Unit Resistivity is ohm-meter (Ωm)

DEFINITION OF RESISTIVITY

From the equation ρ = RA/L, if we take a conductor of unit length (L= 1) and unit area of cross section (A= 1) then 
ρ = R x 1/1
ρ = R

So,Resistivity is the resistance of a material of unit length and unit area of cross-section.

RESISTIVITY OF DIFFERENT MATERIALS 
J

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