I have a hard time in understanding the direction of current. Let there be two points A and B such that the two points are connected by wire. A has higher potential than B. So the electrons flow from A to B. How is the direction of current measured. Is it positive or negative ? Also what is the exact definition of current? Is it defined as the rate of flow of positive charge per unit time or negative charge per unit time? Now let us consider a cell. It has two terminals positive P and negative N. How do the electrons flow? From P to N or from N to P? My textbook says that negative charges flow from P to N. P has higher potential than N and so electrons naturally flow. If that is the case how do the electrons on reaching N again go to P inside the cell because N has lower potential than P? Is there any mechanism going in the cell?