Explain the following :
(a) Why is tungsten used almost axclusively for filament of incandescent lamp ?
(b) Why are the conductors of electric heating devices, such as toaster and electric irons, made of an alloy rather than a pure metal ?
( c) Why is the series arrangement not used for domestic circuits ?
(d) How does the resistance of a wire vary with its cross-sectional area ?
(e ) Why are copper and aluminimum wires usually employed for electricity transmission.