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If two charged bodies of different potentials are placed one beside the other, the charges will not move from one body to the other. But if the two bodies are connected using a conductor, the flow of charges takes place. Charges will flow as long as there is potential difference between the two bodies. This rate of flow of electric charge is called 'electric current'.
A conductor having excess electrons is said to be at a negative or at a lower potential and that having less electrons is said to be at a positive or at a higher potential. Under ordinary conditions the free electrons in a conductor move randomly in such a way that the net flow of charge across any section of the conductor is zero, no current exists in a conductor. If a potential difference is applied between the ends of conductor, the electrons are urged to flow from a point of lower potential to a point of higher potential. Thus there is a net flow of charge in this direction and hence a current flows in the opposite direction to that of electrons. Conventionally, the electric current is said to flow from a higher potential to a lower potential while the electrons flow from a lower potential to a higher potential i.e., the electric current flows in a direction opposite to the flow of electrons.
A simple way of maintaining potential difference between the two ends of a conductor is by connecting it to a battery or a dry cell. In a cell/battery the potential difference between its two electrodes is maintained by the chemical processes between its electrodes and the electrolyte. Therefore a cell is able to maintain a potential difference across a conductor.
The rate of flow of charge is called electric current or in other words the magnitude of the current I is the charge flowing in the circuit in one second. Mathematically expressed,
I= 
Where 'Q' is charge and 't' stands for time.
The unit of electric current is 'ampere' (A).
1 ampere = 1coulomb/second One ampere of current flow through a conductor, if one coulomb of charge flows in one second.
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