DC circuits deals with two primitive quantities, which we will refer to as:
1. Potential(or voltage), and
2. Current.
Current is the actual flow of charged carriers, while difference in potential is the force that causes that flow. As we will see, potential is a single-valued function that may be uniquely defined over the nodes of a network. Current,on the other hand, flows through the branches of the network. Figure below shows the basics of a branch, in which a voltage is defined across the branch and a current is defined to flow through the branch. A DC circuit is a collection of such elements, connected together by wires.
