WHAT IS ELECTRIC CURRENT ?Electric current is expressed by the amount of charge flowing through a particular area in unit time. In other words, it is the rate of flow of charges. Flowing charge constitute of Electrons. However, electrons were not known at the time when phenomenon of electricity was first observed.
THE DIRECTION OF ELECTRIC CURRENTElectric current was considered to be the flow of positive charges and the direction of flow of positive charges is taken as the direction of electric current. Conventionally, in an electric circuit thedirection of electric current is taken as oppositeto the direction of flow of electrons, which are negatively charged.
EQUATION FOR THE ELECTRIC CURRENTIf a net charge Q , flows across any cross- section of a conductor in time t, then the current I, through the cross section is I=Q / t
SI UNIT OF ELECTRIC CHARGE & ELECTRIC CURRENTThe SI unit of electric charge is coulomb (C),which is equivalent to the charge contained in nearly 6 X 10 18 electrons. The electric current is expressed by a unit called ampere (A), named after the French scientist, Andre- Marie Ampere. One ampere is constituted by the flow one coulomb of charge per second, that is, 1A= 1C/1s.
HOW SMALL QUANTITIES OFELECTRIC CURRENT ARE EXPRESSEDThe small quantities of electriccurrent are expressed in :-(i) Milliampere (1mA = 10 -3 A)(ii) Microampere (1µm = 10-6 A).
HOW ELECTRIC CURRENT MEASURES ? An instrument called ammetermeasures electric current in a circuit. It is always connected in series in a circuitthrough which the flowing current can be measure. It is indicated by the capital letter A, in a electric circuit.