$(a)$ Why is the series arrangement not used for domestic circuits?
$(b)$ Why is tungsten used almost exclusively for the filament of electric lamps?
$(c)$ Why are the conductors of electric heating devices,such as bread toasters and electric irons,made of an alloy rather than a pure metal?
$(d)$ Why are copper and aluminium wires usually employed for electricity transmission?
$(e)$ Why does the cord of an electric heater not glow while the heating element does?

(N/A) In a series arrangement,if any one component stops working,the circuit breaks,and none of the other devices will function.
$(b)$ Tungsten is used because it has a very high melting point $(3380 ^\circ C)$ and high resistivity,allowing it to emit light without melting.
$(c)$ Alloys have higher resistivity than pure metals and do not oxidize (burn) easily at high temperatures,making them ideal for heating elements.
$(d)$ Copper and aluminium have very low resistivity,which minimizes energy loss during the transmission of electricity.
$(e)$ The cord has very low resistance,so it produces negligible heat,whereas the heating element has high resistance,causing it to glow due to the heating effect of current.