The English Scientist William Gilbert in the Sixteenth Century Found that some substances acquire the propety of Attraction the light bodies when rubbed with some paticular substances. The Substance on acquiring this property is said to be charged. Charge an be Positive or Negative.

                                                                William Gilbert

Basically, Electric Current is simply a flow of Charges. A metallic conductor contain free charges which move when a force is excerted on them by an Electric fild . These charges are Negative electrons. The Electric charge flow from Higher Potential to Lower potential.




IMPORTENT POINTS 

1. Like Charges Repel Each Other
2.Unlike Charges Attract Each Other
3.SI Unit Of Electric Charge is COULOMB
                     It is Denoted by Letter (C)



We can Define this Unit Of  Charge as Follows:
  
One Coulomb is That Quantity of Electric Charge Which excert a Force of  9 x 10 to the power 9 Newtones on an Equal Chaege placed at a distance of 1 meter fome it. 

          NUMERICAL

1. Calculate the Number of Electrons constituting one Coulomb of Charge

Solution : We know that the charge of an Electron is 1.6 x 10-19 Coulomb
                    
                       Now, If charge is 1.6 x 10-19 C 
                       So, if Charge is 1C , then No. of Electron = 1/1.6x10-19 * 1
                                                                                              
                                                                                           = 10^19 / 1.6
                                                                                           = 10/1.6 * 10^18
                                                                                           = 6.25 * 10^18

Thus, 6.25 x 10^18 Electron taken together contribute 1 Coulamb Charge.

The Above Example Tells us that the SI unit of Coulomb (C) is Equivalent to the charge contained in 6.25 x 10^18 Electrons