Electric Current, Unit of Current


  • The electrical current is defined as the rate of flow of charge in particular direction.


  • It is defined as the net flow of charge that passes through any cross-sectional area in a unit time.

       I = Q / t

       I = dQ / dt


      I = Current

    Q = Charge

     t = Time

  • In earlier time, it was thought that the current is flows due to positive charge when electrons were not known. 
  • It was realized that the electrons are responsible for flow of current after discovery of electrons. 
  • The direction of positive charge from positive terminal of battery to negative terminal is taken as the direction of the conventional current.
  • We can say that the direction of conventional current is opposite to the direction of electrons. 
  • The direction of electrons as conventional current is shown in the figure.


One ampere current

  • If a one coulomb of charge flows through conductor in a one second, the electrical current flowing through conductor is called as one ampere.

Unit of current

        I = Q / t

  • The SI unit of charge is coulomb and time is second therefore the SI unit of current is charge / second or ampere.
  • 1 mA = 10 – 3 ampere
  • 1µA = 10 – 6 ampere
  • 1nA = 10 – 9 ampere

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