# 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