Question

pls explain in detail Example no.12.5 of ncert science book pg. no. 208 of class 10

Answer 1

Given that
Resistance of wire=26ohm
Diameter of wire=0•3mm=3×10power4
Length of wire=1 m
Now,
Resistivity=resistance×area/length
Area=22/7×radius×radius
=22/7×3×10power4/2
Now,Resistivity=resistance×area/length
=26ohm×22/7×3×10power4×3×10power4/4×1
=1•84×10power6 ohm metre.
So this is the resistivity of manganese.

Answer 2

Resistance of wire- 26 ohms. Diameter of wire- 0.3 mm len gth of wire- 1m and relation of R=rho×l\A

Rho= RA/l=Rπd×d/4l

Substitution of values in this gives

Rho =1.84×10power 8ohms m

The resistivity of the metal at 20°c is 1.84× 10power 8 ohms .