Tell about Electric Currents ?

In these devices photonic energy from sunlight is absorbed by electrons and converted into electrical energy.

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

Most of the electricity that we use comes in the form of alternating current (AC) from the electric power grid

Electric current is measured using a device called an ammeter

Alternating current is produced by electric generators that operate on Faraday’s Law of Induction, by which a changing magnetic field can induce an electric current in a conductor.

Electric currents cause Joule heating, which creates light in incandescent light bulbs. They also create magnetic fields, which are used in motors, inductors and generators.

Generators have rotating coils of wire that pass through magnetic fields as they turn

The moving charged particles in an electric current are called charge carriers. In metals, one or more electrons from each atom are loosely bound to the atom, and can move freely about within the metal. These conduction electrons are the charge carriers in metal conductors.

As the coils rotate, they open and close with respect to the magnetic field and produce an electric current that reverses direction every half turn.

The current goes through a complete forward-and-reverse cycle 60 times each second, or 60 hertz (Hz) (50 Hz in some countries). Generators

The conventional symbol for current is I, which originates from the French phrase intensité du courant, (current intensity).[4][5] Current intensity is often referred to simply as current

The I symbol was used by André-Marie Ampère, after whom the unit of electric current is named, in formulating Ampère's force law

The notation travelled from France to Great Britain, where it became standard, although at least one journal did not change from using C to I until 1896

In a conductive material, the moving charged particles that constitute the electric current are called charge carriers

In metals, which make up the wires and other conductors in most electrical circuits, the positively charged atomic nuclei of the atoms are held in a fixed position, and the negatively charged electrons are the charge carriers, free to move about in the metal.

In other materials, notably the semiconductors, the charge carriers can be positive or negative, depending on the dopant used.

Positive and negative charge carriers may even be present at the same time, as happens in an electrolyte in an electrochemical cell.

A flow of positive charges gives the same electric current, and has the same effect in a circuit, as an equal flow of negative charges in the opposite direction

Since current can be the flow of either positive or negative charges, or both, a convention is needed for the direction of current that is independent of the type of charge carriers

The direction of conventional current is arbitrarily defined as the same direction as positive charges flow

Since electrons, the charge carriers in metal wires and most other parts of electric circuits, have a negative charge, as a consequence, they flow in the opposite direction of conventional current flow in an electrical circuit.

Since the current in a wire or component can flow in either direction, when a variable I is defined to represent that current, the direction representing positive current must be specified, usually by an arrow on the circuit schematic diagram.

This is called the reference direction of current I. If the current flows in the opposite direction, the variable I has a negative value.

When analyzing electrical circuits, the actual direction of current through a specific circuit element is usually unknown.

Consequently, the reference directions of currents are often assigned arbitrarily