Current

•   While the potential difference among two charges forces a third charge to move, the charge in motion is known as current.
•   Therefore, to generate current charge ought to be moved by a potential difference.
•   In solid materials, as copper wire, the free electrons are charges that might be forced to move with relatively easy by a potential difference, they are needed a little work to be moved. As illustrated in given figure. If a potential difference is linked across two ends of a copper wire the applied voltage forces the free electron to move.

• From the point of negative charge at one of end, this current is drift of electrons and returning to the positive charge at the other end.
• In the middle row each electron is numbered, corresponding to a copper to which this electron belongs.
• Considering the only case of one electron moving, note down that the electron returning to the positive side of the voltage source is not electron S which left negative side.
• All of electrons are similar. The drift free electrons, therefore, resulted in the charge of one electron moving through the wire.
• In motion this charge is current.
• Current is the steady flow of electrons.
• just the electrons move, not the potential difference.
• The current ought to be the similar at all of points of the wire at all times.

Another definition of current may be made as

• Consider q(t) be the overall charge that has passed a reference point as an arbitrary time t=0, moving in the declared direction. A contribution to this net charge will be negative on the condition when the negative charge is flowing in the reference direction. 
• As the given figure indicate a history of net charge q(t) that has passed a given reference point in a wire.

• The current at a particular point and flowing in a mention direction as the instantaneous rate at which total positive charge is moving past the point in the indicated direction.
• I or i is symbol of current.

      Mathematically it may be given as

                                                                I = dq/dt

Graphical Symbols for Current