Question

On what factors resistance of a wire depends.derive an expression for it

Answer 1

the resistance depends upon resistivity of the material, length, temperature, and area of cross-section.
Mathematically, R=pl/A where p is the resistivity,l is the length and A is area of cross section.
from above, p = RA/l = ohm*m2/m = ohm-metre.
hence SI unit of resistivity id ohm-metre

Hope it helps uh

Answer 2

factors
1.length of the conductor
2.cross section of the conductor
3.temperature

Expression::
resistance is directly proportional to the length of the conductor
R is directly propertional to l
R is directly proportional to 1/a
there fore
R is directly proportional to l/a
proportionality constant RO
R=£l/a
£= ro = resistivity