Q.State Kirchhoff's junction rule and Kirchhoff's loop rule for an electrical network. Name the physical conservation principle that each rule expresses.

Kirchhoff's Laws and Circuit Analysis

Complex circuits that cannot be reduced to simple series–parallel combinations are solved with Kirchhoff's two rules:

• Junction (current) rule — the algebraic sum of currents meeting at a node is zero, $\sum I = 0$. It expresses conservation of charge.
• Loop (voltage) rule — around any closed loop the algebraic sum of EMFs and $IR$ drops is zero, $\sum \varepsilon = \sum IR$. It expresses conservation of energy.

To apply them, assign a current to each branch, write one junction equation per independent node and one loop equation per independent mesh, and solve the simultaneous equations; a negative answer simply means the assumed direction was reversed. Where node potentials are given, the current in a branch follows directly from Ohm's law, $I=(V_1-V_2)/R$, and the junction rule fixes an unknown branch current from the others. …