The number of free electrons are available in conductors and semiconductors. In the absence of electric field, these free electrons moves in random directions shown in figure.
When an 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 electric current flows if the circuit is closed.
(The SI unit of electric current is Ampere. It is denoted by I)
Conventional current and electron current
The current flows from the positive terminal of the battery to the negative terminal of the battery are called conventional current.
The current flows from negative terminal of the battery to the positive terminal of the battery is called electron current. In metals, current is caused by electrons and such kind of current is known as electric 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 be stepped up or stepped down.
- AC Current can be generated at higher voltage.
DC stands for direct current. Direct current has constant magnitude and direction.
- DC Current cannot be stepped up or stepped down.
- DC Current cannot be generated at high voltages due to commutation problems.
Properties of Electric Current
When electric current flows through a high resistive material heat is produced. This property of electric current is used in various heating devices, such as stoves, radiators, water heaters, welding, electric lamps, arc furnaces etc.
When electric current passes through a coil, a magnetic field is produced. Magnetic properties of an electric current are utilized in various electrical machines. Such as electric generators, electric motors, relays etc.
When electric current passes through an electrolyte, chemical action takes place. The electro-chemical properties of an electric current is utilized in electro-chemical industries for various applications such a electro-plating, electrolytic refining, electro-deposition etc.