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.

It is clear that 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 on the wire from one plate to another.In fact from our every day 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 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”.

SOURCES OF CURRENT: -

                    “A device which supplies current by maintaining a potential difference between two terminal points is called source of current”.

                    Every source of current convert non-electrical energy to electrical energy, some sources of current are given below.

1.                     ELECTRIC CELL: - It convert chemical energy; into electrical energy. Dry cell and automobile battery are the best examples of primary and secondary cells.

2.                     ELECTRIC GENERATORS: - It converts mechanical energy into electrical energy.

3.                     THERMOCOUPLES: -They converts heat energy into electrical energy.

4.                     SOLAR CELLS: - They convert sunlight into electrical energy.

EFFECTS OF CURRENT: -

                    When current is passed through certain medium it produces some effects the obvious effects are:

1.                     Heating effect

2.                     Magnetic effect

3.                     Chemical effect

1)                     HEATING EFFECT: - When current is passes through a metallic wire, the electrons do some work against the resistance of the wire. This work appears in the form of heat. The heating effect of current is utilized in electric heater, hair drier, kettles toaster and electric iron.

2)                     MAGNETIC EFFECT: -       Oersted discovered that a current carrying conductor deflects a compass needle when it is placed near it. Thus a current carrying conductor produce a magnetic field around itself and this is called the magnetic effect of current

3)                     CHEMICAL EFFECT: - When current is passed through electrolyte a chemical reaction take place this is called chemical effect of current.