Write the necessary facts to understand Kirchhoff's laws.

(N/A) $1$. In a given circuit or network,the direction of current is indicated by using an arrow $(\rightarrow)$.
$2$. The source of $EMF$ or a cell is represented with a positive terminal $(P)$ and a negative terminal $(N)$.
$3$. For a cell discharging,the potential difference is given by $V = V(P) - V(N) = \varepsilon - Ir$.
$4$. When a cell is being charged,the potential difference is given by $V = \varepsilon + Ir$.