Nodes, Branches and Loops

When we discuss network topology we have to understand certain terms. Among these terms node, branch or loops are used most of the time. Let�s see what they mean.

Branch: A single element with its terminals is usually called a branch. For example a voltage source or a resistor is a branch.

Node: When two or more branches are connected at a point then that point is called a node.

Loop: A closed path in a circuit is called a loop.

Mesh: Mesh is a kind of loop which has no loop inside it. But you have to remember that all meshes are also loops. But all loops are not meshes. 

For example let�s have look at the following figure:

In a network or circuit, number of loop, nodes and branches has to satisfy the following fundamental relationship:

                b=l+n-1

where, b = number of branches,

l = number of loops and

n = number of nodes.

There is another important thing to remember in circuit analysis. 

01.   In a series connection two or more elements are connected sequentially, so they carry the same current I , that is in a series connection current will always remain constant where as voltage will have a drop after each element.

02.   In a parallel connection, all the branches are connected at two common nodes. So, they apparently have the same voltage at each node but the current is divided according to ohm�s law.