Question

(a) List the factors on which the resistance of a conductor in the shape of 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.

Answer 1

(a) Resistance of a conductor depends directly on its length and is inversely proportional to the area of cross-section.
(b) Metals have free electrons and they can move and conduct electricity, whereas glass does not allow electrons and charges to flow freely and hence it is an insulator.
(c) The resistivity of an alloy is generally, higher than that of its constituent metals. Alloys do not oxidise (burn) readily, at higher temperatures. Therefore, conductors of electric heating devices, such as toasters and electric irons, are made of an alloy rather than pure metal.