Electric Currents in Conductors
An electric current is a flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire.
It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma.
The SI unit for measuring an electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second. Electric current is measured using a device called an ammeter
current is the rate at which charge flows past a point on a circuit. As depicted in the diagram below, the current in a circuit can be determined if the quantity of charge Q passing through a cross section of a wire in a time t can be measured.
The current is simply the ratio of the quantity of charge and time.
Types of Electric Current
1 Direct Current :Its direction and magnitude do not change with time .
2 Alternating current :
its magnitude change continuously and change its direction periodically is called alternating current.
The electric current flowing per unit area of cross –section of conductor is called current density
Current density (j) = I / A
Its SI unit is ampere m-2