A simple electric circuit, where current is represented by the letter i. The relationship among the voltage (V), resistance (R), and current (I) is V=IR; this is called as Ohm''s Law.An electric current is a flow of electric charge by an electrical conductor. Electric charge flows when there is voltage present across a conductor.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 like as in a plasma.The SI unit for measuring an electric current is the ampere, which is the flow of electric charges by a surface at the rate of one coulomb per second. Electric current can be measured by using an ammeter.Electric currents cause many effects, notably heating, but also induce magnetic fields, which are widely used for inductors, motors, and generators.