Producing a diagram of an electrical circuit is a very important step in solving
electrical circuit problems. The diagram below shows the circuit symbols for a cell
and a resistor. It shows the e.m.f. (E) produced by the cell, the current (I) flowing
through the circuit and the voltage drop (V) which occurs across the resistor.
The direction of the arrow representing the e.m.f., points from the negative terminal of the cell (smaller line), to the positive terminal (larger line). The current is flowing from the positive terminal towards the negative, (conventional current flow). The arrow representing the voltage dropped across the resistor, is pointing in the opposite direction to the current flow, it points towards the end of the resistor which is at a higher potential.
There are often several components of the same type in one circuit and there can be several different voltages and currents. Subscript notation is used to identify each of the different components, voltages and currents etc. in the circuit. See diagram below.