CBSE Class 12 · 2007 · Current ElectricityShort Answer

\textbf{Junction rule:} at any junction the sum of currents entering equals the sum leaving ($\sum I=0$) — conservation of charge. \textbf{Loop rule:} the algebraic sum of potential changes around any closed loop is zero ($\sum \Delta V=0$) — conservation of energy. Assigning loop currents and applying the loop rule to the given network yields the branch current (e.g. $I=-1.2\text{A}$, the minus sign indicating the actual direction is opposite to the one assumed).