CURRENT ELECTRICITY

ELECTRIC CURRENT

“The rate of flow of charge is called as current”. Mathematically it can be expressed as

                                                I = Q / t

Where I represent the current, Q is the charge which passes through certain area of cross section in time t.

UNIT: - The unit of current is Ampere and Ampere is defined as,

                        “If one coulomb of charge flows through any cross-section of a Conductor in one second”

DIRECTION OF ELECTRIC CURRENT: -Let’s consider that a capacitor connected to a voltage source. The charges are static.  Now if we connect  the two plates by a conducting wire, Then charge will flow from one plate to another to neutralize it. But here think that how we can say the charges moved along the wire from one plate to another.

            In fact from our everyday life we know that always flow take place from high to low potential, that is why the old investigator’s decided that in this case the same principle is valid i.e. charge flow from high potential (positive) to low potential (negative). In other words according to their idea the positive charges left the plate, crossed along the wire and neutralized the negative charges on the other plate. Hence this type of current is called CONVENTIONAL CURRENT.

            But now a day it is incorrect, because current through a metallic wire is due to the motion of free electrons. In case of liquids and gases the current is transported both by positive and negative charges, while in case of accelerator the current may be transported due to flow of positive charges.

 DRIFT OF ELECTRONS IN METALLIC CONDUCTORS: - A metallic wire consists of large number of free electrons. Therefore electrons move randomly in such a way, that net current in the wire is zero, as shown in the figure. Now if potential difference is applied, so electric field is set-up at every point in the wire, due to which all the free electrons.

DRIFT OF ELECTRONS IN METALLIC CONDUCTORS: -

                    A metallic wire consists of large number of free electrons. Therefore electrons move randomly in such a way, that net current in the wire is zero. Now if potential difference is applied, so electric field is setup at every point in the wire, due to which all the free electrons. Experience a force qE in a direction opposite to E. As a result of this force and the continuous collision of Electrons with atom, the electron acquires a net drift velocity.

                                                                                               

DRIFT VELOCITY: -

                    “The mean velocity gained by electrons in an atom when electric field is setup inside it is called drift velocity”.