Electric Current

Most of the electric current around us us bound in neutral atoms.It is not easy to overcome the electrostatic force of attraction between the nuclei and electrons in at atom.How,ever in metals some electrons are not tightly bond to the nuclei and are free to move around randomly.They have weak force between them and nucleus.Similarly in solutions some positive and negative charges can freely move around randomly.When such free charges are exposed to an external electric field,they move in specific direction and thus constitute current.

Electric current is produce due to the flow of either positive charge or negative charge or both of charges at same time.In metals the current is produced only due to the flow of free electrons I.E negative charges.In case of electrolyte its molecules in aqueous solution dissociate among positive and negative ions.So the current in electrolyte is produced due to the flow of bot positive and negative charges.

"THE RATE OF FLOW OF ELECTRIC CHARGE THROUGH ANY CROSS SECTIONAL AREA IS CALLED CURRENT"

If the Q is passing through any cross sectional area in time t,then current I flowing through it will be given by

CURRENT=CHARGE/TIME

I=Q/T

SL unit of current is Amperes (A).

If a charge of one coulomb passes through a cross sectional area in one second then the current is one ampere.Smaller units of current are Milli Amperes (mA),Micro Ampere (uA),which are defined as:

1mA=10^-3 A

1uf=10^-6 A

Battery is one of the source of current.The electrochemical reactions inside a battery separates positive and negative electric charges.The separation of charges setup potential difference between the terminals of the battery.When we connect a conducting wire across the terminals of battery,the charges can move from one terminal to the other due to the potential difference.The chemical energy of the battery changes to electrical potential energy.The electrical potential energy decreases as the charges move around the circuit.This electrical potential energy can be converted to other useful forms of energy such as Heat Energy,Light Energy,And Sound Energy.It is only the energy which changes form but the number of charge carries and the charge on each carrier always remain the same i.e charge carries are not used up.Instead of electrical potential energy we use the term electric potential which is potential energy per unit charge.