(a) List the factors on which the resistance of a conductor in the shape of a wire depends.
(b) Why are metals good conductors of electricity whereas glass is a bad conductor of electricity? Give reason.
(c) Why are alloys commonly used in electrical heating devices ? Give reason.
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
(ii) The resistance of a conductor is inversely proportional to the area of the cross-section of the conductor.
(iii)Resistance also depends on a material of the conductor
(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.
