Electric Current, Unit of Current

 

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

                                                   OR

• 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

Where

      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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