What determines the rate at which energy is delivered by a current?

$A$ 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?

Explain the following.
$(a)$ Why is the series arrangement not used for domestic circuits?
$(b)$ How does the resistance of a wire vary with its area of cross-section?

How can three resistors of resistances $2\, \Omega$,$3\, \Omega$,and $6\, \Omega$ be connected to give a total resistance of $1\, \Omega$?

How much energy is given to each coulomb of charge passing through a $6\, V$ battery (in $, J$)?

What is meant by saying that the potential difference between two points is $1$ $V$?