Nodal analysis is a systematic method used in electrical engineering to determine the voltage at each node in a circuit with respect to a reference node (ground). This technique is based on Kirchhoff’s Current Law (KCL), which states that the sum of currents entering a node is equal to the sum of currents leaving the node. Nodal analysis is particularly useful for analyzing circuits with multiple nodes and branches, such as complex resistive networks or AC circuits with passive components.

Here’s a step-by-step guide to performing nodal analysis for an electric circuit:

- Select a reference node (ground): Choose a node with the highest number of connected elements or the most complex connections as the reference node. This node will have a voltage of 0 V by definition.
- Label unknown node voltages: Assign a variable (e.g., V1, V2, V3, etc.) to the voltage at each remaining node with respect to the reference node.
- Apply KCL at each unknown node: Write KCL equations for each node with an unknown voltage by expressing the sum of currents entering the node as the sum of currents leaving the node. In these equations, express branch currents in terms of node voltages and component values (such as resistances or impedances).
- Solve the equations: Use algebraic techniques, such as substitution, elimination, or matrix methods, to solve the system of linear equations obtained in the previous step. The solutions will provide the unknown node voltages.
- Calculate branch currents and other quantities: Once the node voltages are known, calculate the currents through each component and any other desired circuit quantities using Ohm’s Law or other relevant formulas.

For AC circuits with passive components (resistors, inductors, and capacitors), nodal analysis can be performed using complex impedances. In this case, replace resistances with complex impedances (Z = R + jX) and express voltages and currents as complex phasors. The same steps can be followed to analyze the circuit, and the resulting node voltages will be complex phasor values, from which magnitudes and phases can be determined.

Nodal analysis is a powerful technique for analyzing electric circuits with multiple nodes and branches, providing a systematic approach to determine node voltages and other circuit quantities.

## Other Circuit Theorems

Circuit theorems are essential tools for analyzing and simplifying complex electrical circuits. These theorems help engineers and technicians find equivalent circuits, solve for unknown quantities, and optimize circuit performance. Some of the most important circuit theorems include: