What are the essential requirements of a heater filament?

An electric refrigerator rated $400 \ W$ operates $8 \ h$ per day. What is the cost of the energy to operate it for $30$ days at ₹ $3.00$ per $kWh$?

$(a)$ What material is used in making the filament of an electric bulb?
$(b)$ Name the characteristics which make it suitable for this.

$(a)$ 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?

Mention one reason why tungsten is used for making the filament of an electric lamp.

If an electric current $I$ flows through a resistor $R$ in a circuit for time $t$,then the electrical energy $W$ consumed is given by: