Question

Question 19:
(a) Give one example to show how the resistance depends on the nature of material of the conductor.
(b) Calculate the resistance of an aluminium cable of length 10 km and diameter 2.0 mm if the resistivity of aluminium is 2.7 x 10-8Ωm.

Lakhmir Singh Physics Class 10

Answer 1

Answer:

(a) The resistance will be lower in the case of a metal because it has free electrons, unlike non-metals who show more resistance and are bad conductors. Even metals like lead show higher resistance due to lower presence of free electrons but metals like silver have higher presesnce of free electrons so they show lesser resistance.

(b) The resistance in a conductor of cross sectional area (A) and length (L) can be found by the formula

$\frac{rho \times l}{a}$

where rho is the resistivity, l is the length and a, is the area.

Further the calculations can be made by the app "photomath".

Note: first change all units to the same SI unit.