In this section we shall develop a general method of circuit analysis in which voltages are the unknowns to be found. A convenient choice of voltages for many networks is the set of node voltages. Since a voltage is defined as existing between two nodes, it is convenient to select one node in the network to be a reference node and than associate a voltage at each of the other nodes. The voltage of each of the nonreference nodes with respect to the reference node is defined to be a node voltage. It is common practice to select reference directions for these voltage so that the plus ends are all at the nonreference nodes and the minus ends all at the reference node. For a circuit containing N nodes, there will be N-1 nonreference nodes and thus N-1 node voltages. Nodal analysis is a method in which we will break the circuit, that is, solve for key set of circuit variables, by finding the node voltage themselves. Any other current or voltage will follow easily once the circuit is broken.