The number of free electrons is available in conductors and semiconductors. In the absence of electric field, these free electrons moves in random directions shown in figure. There is no conduction of electric current.
When electric field is applied to the conductors and semiconductors, the free electrons start moving in a particular direction and it constitutes an electric current.
Definition of electric current
The rate of flow of electric charge through any section of wire is called electric current. The current will flow if the circuit is closed.
The SI unit of current is Ampere. It is denoted by IAn electric current is defined by Andre-Marie Ampere. Hence the unit of electric current, the Ampere, was named after him. He is a French mathematician and physicist, laid the foundation of electrodynamics. Ammeter is also invented by Ampere.
Conventional current and Electron current
The current flows from positive terminal of the battery to negative terminal of the battery,such current known as conventional current.
The current flows from negative terminal of the battery to positive terminal of the battery is called electron current. In metals, current is caused by electrons and such current known as electron current.
Types of Electric Current
An electric current is divided into AC current and DC current.
AC stands for Alternating Current. Alternating Current changes its direction and magnitude w.r.t time or at regular intervals.
- AC Current can step up or step down the voltage.
- AC Current can generate at higher voltage.
DC stands for direct current. Direct current has constant magnitude and direction.
- DC Current cannot step up or step down the voltage level.
- DC Current cannot generate at high voltages, due to commutation problems.
Properties of Electric Current
When current flows through a material having very high resistance, heat is produced. This property of current is used in various heating devices, such as stoves, radiators, water heaters, welding, electric lamps, arc furnaces etc.
When current passes through a coil, magnetic field is produced. Magnetic properties of current are utilized in various electrical machines. Such as electric generators, electric motors, relays etc.
When current passes through an electrolyte, chemical action takes place. The electro-chemical properties of current utilizes in electro-chemical industries for various applications such a elector-plating, electrolytic refining, electro-deposition etc.