what is the difference between resistance and resistivity ?
Resistivity is the obstruction offered to the flow of current by UNIT AREA OF the conductor.
So basically, resistance is the property of the object (say a copper wire), whereas resistivity is the property of the substance (copper).
And so resistance depends upon the properties of the object.
Whereas resistivity depends upon the properties of the metal.
So for example take two objects A and B made of aluminium. Both are of a different size.
The resistance of A & B will be different.
But the resistivity will be the same.