An electric heater of resistance $8 \, \Omega$ draws $15 \, A$ from the service mains for $2$ hours. Calculate the rate at which heat is developed in the heater (in $W$).

$A$ hot plate of an electric oven connected to a $220\, V$ line has two resistance coils $A$ and $B$,each of $24\,\Omega$ resistance,which may be used separately,in series,or in parallel. What are the currents in the three cases?

Draw a schematic diagram of a circuit consisting of a battery of three cells of $2\, V$ each,a $5 \,\Omega $ resistor,an $8\,\Omega $ resistor,and a $12\,\Omega $ resistor,and a plug key,all connected in series.

Explain the following.
$(a)$ Why is tungsten used almost exclusively for the filament of electric lamps?
$(b)$ Why are the conductors of electric heating devices,such as bread-toasters and electric irons,made of an alloy rather than a pure metal?

What does an electric circuit mean?

Why are coils of electric toasters and electric irons made of an alloy rather than a pure metal?