Question

Define resistivity . Two wires of equal cross sectional area, one of copper and other of maganin have same resistance. which one will be longer why? Given the resistivity of maganin is more than that of copper.

Answer 1

Resistivity is a Resistance of that material ( Conductor ) having cross sectional area equal to 1 meter squared and length of the material should be one meter long...

This means that if you take any material which is One meter long and its area of cross section is 1 meter square then whatever resistance we get from such material will be called its resistivity...

For Different material , resistivity is different but for same material it will not change at all...No matter if you stretch the material or elongate it...or make it shorter..its resistivity will remain same...But if you change the material..Resistivity will definitely going to change..This is because the Resistance is different for different materials...

For example...If you take two copper rods...both having length 1m and 10m or you may also consider rods with different diameters...the resistivity for the both copper rods will remain same...

But if you take copper rod and silver rod of same dimensions then resistitvity for both the material is different...

So for the same material, Resistivity remain same and for different material it will be changed... hope this help you....

Answer 2

Resistivity can be defined as a measure of how strongly a material opposes the flow of electric current.
Resistivity is different for different materials and remains unchanged however may you stretch the wire or compress it.
Symbol of resistivity is Rho "ρ" or Ohm Meters "Ω m"

If 2 wires of equal cross sectional area have same resistance,
R1= ρ1×L1/A1
R2= ρ2×L2/A2
Since, A1=A2 and R1=R2,
ρ1×L1 = ρ2×L2

Now, if ρ1 > ρ2,
L1 < L2 and vice versa.