Circuit Nodes and Loops

Overview

This lesson explains the concepts of nodes and loops in electrical circuits, focusing on definitions, identification, and practical examples.

A node is a junction point where two or more circuit elements connect.
Circuit elements include resistors, power supplies (voltage or current), capacitors, and inductors.
Wires are not considered circuit elements and do not form nodes.
The reference node, often called the "ground node," is typically where multiple elements connect to the circuit's ground.
In complex circuits, all points connected by wires without circuit elements between them make a single node.
Example circuits may have three or four nodes depending on how resistors and supplies are connected.

To count nodes, look for connection points between two or more elements (not wires).
In typical example circuits, reference or ground is counted as one node.
Rearranging circuit drawings may clarify node locations but does not change the number of nodes.
In this course, only basic elements like resistors, capacitors, inductors, and voltage/current supplies are covered.

A loop is a closed path in a circuit that passes through two or more circuit elements.
To identify a loop, start at any point and follow a path through connected elements back to the starting point.
Circuits can have multiple loops, including inner loops and an outer loop.
When analyzing circuits, use arrows to indicate current direction (preferably all clockwise or all counter-clockwise for consistency).

Node — Junction where two or more circuit elements (not wires) meet.
Circuit Element — Components like resistors, power supplies, capacitors, or inductors.
Reference Node/Ground — The node used as a common voltage reference point.
Loop — Closed path in a circuit containing at least two circuit elements.

Review circuit diagrams and practice identifying nodes and loops.
Prepare for the next lesson, which will cover using nodes and loops for circuit analysis.