# Reference Node and Node Voltages

Reference Node
In circuits, we usually label a node as the reference node also called ground and define the other node voltages with respect to this point. The reference node has a potential of $0 V$ by definition. The following symbol is used to indicate the reference node:

The Reference Node Symbol

As mentioned, the selection of the reference node is arbitrary. However, a wise selection can make the solving easier. As a general rule, it is usually chosen to be

# Problem 1-10: Solving by Nodal Analysis - Circuit with Four Nodes

Solve the circuit by nodal analysis and find $V_a$.

Solution
a) Choose a reference node, label node voltages:

Solve the circuit using nodal analysis and find the power of $Is_1$.