. Explain the following
i. Why is tungsten used almost exclusively for filament of electric lamps
ii. Why are copper and aluminium wires usually used for electricity transmission
Ans: i. Tungsten is used almost exclusively for filament of electric lamps because its melting point is extremely high (3380°C). As a result, on passing current tungsten filament gets very hot and emits light
ii. Copper and aluminium wires are commonly used for electricity transmission because resistivity of these two materials are quite small. Moreover, their density is comparatively not very high and hence mass of transmission wire is not very high. As a result, cost is manageable.