The resistance of a conductor depends on the following factor:

(i) The resistance of a conductor is directly proportional to length (l) of the conductor $R\propto \mathcal{l}$

(ii) The resistance of a conductor is inversely proportional to the area of the cross-section of the conductor.

$R\propto \frac{I}{A}$

(iii)Resistance also depends on a material of the conductor

$\therefore R= \rho \frac{\mathcal{l}}{A}$

(iv) Resistance and resistivity also depend on temperature.

(b) Metal are good conductors of electricity because they have free electrons to conduct electricity. Whereas glass does not have free electrons hence it is a bad conductor of electricity.

Alloys have a high resistivity in comparison to pure metals. Therefore, alloys are used for making coils for electric heating devices rather than a pure metal.

Resistance (R) = Slope of line =

The advantages of electricity as compared to other forms of energy is as follows:

(i) Electricity can be readily transmitted over large distances with relatively small loss in energy.
(ii) Electricity can be easily converted to other forms of energy ike heat, light, sound, motion, etc.
(iii) electricity is the most convenient source of energy.

Electricity playing an important role in modern society has a wide range of applications:

(i) Electricity is used in heating, lighting, cooking, operating fans, geysers, etc. in our houses, hospitals, hotels, office buildings, food storage plants.

(ii) Electricity is used in industries to run various types of machines.

(iii) In transportation to pull electric trains, trams, etc. 

(iv) Electricity is used for irrigation purposes in agriculture.