Definition and Units of Electric Current
- An electric current is a flow of charged particles through a conductor or space.
- It is defined as the net rate of flow of electric charge through a surface.
- The charge carriers in electric circuits are often electrons or ions.
- In the International System of Units (SI), electric current is expressed in units of ampere (A).
- The ampere is an SI base unit and electric current is a base quantity in the International System of Quantities (ISQ).
- Current intensity is commonly referred to as current itself.
- The unit of current is the ampere (A).
- Current is defined as the rate of flow of electric charge.
- It represents the movement of electrons through a conductor.
- Current can be either direct current (DC) or alternating current (AC).

Symbol and Conventions of Electric Current
- The conventional symbol for current is 'I'.
- It originates from the French phrase 'intensité du courant' (current intensity).
- The direction of conventional current is arbitrarily defined as the direction in which positive charges flow.
- Electrons, the charge carriers in an electrical circuit, flow in the opposite direction of conventional current.
- The reference direction of current is usually assigned arbitrarily in circuit analysis.
- The first step in the analysis is assuming reference directions for the unknown currents.
- Reference directions are necessary for determining the direction of current flow in a circuit.
- This assumption simplifies the analysis of circuit equations and helps in solving for the unknown currents.
- Reference directions can be chosen arbitrarily, but consistency is important throughout the analysis.
- Once the reference directions are established, the circuit equations can be formulated and solved.

Ohm's Law
- Ohm's law states that the current through a conductor is directly proportional to the potential difference across it.
- The mathematical equation for Ohm's law is I = V/R, where I is the current, V is the potential difference, and R is the resistance.
- The resistance in Ohm's law is constant and independent of the current.
- Ohm's law is used to calculate the current in a circuit based on the voltage and resistance.
- It is a fundamental principle in electrical engineering.

Alternating and Direct Current
- Alternating current (AC) periodically reverses the direction of electric charge movement.
- AC is commonly used for electric power delivery and transmission.
- The waveform of an AC power circuit is usually a sine wave.
- Direct current (DC) refers to the movement of electric charge in only one direction.
- DC is produced by sources like batteries and solar cells, and it can be converted from AC using a rectifier.

Occurrences and Measurement of Electric Current
- Natural occurrences of electric current include lightning, static electric discharge, and the solar wind.
- Man-made occurrences include the flow of conduction electrons in power lines and electronic equipment.
- Eddy currents occur in conductors exposed to changing magnetic fields.
- Electric currents also occur in conductors exposed to electromagnetic waves.
- Electric current can be measured using an ammeter or a galvanometer.

Electric current (Wikipedia)

An electric current is a flow of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is defined as the net rate of flow of electric charge through a surface. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In an electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons.

Electric current
A simple electric circuit, where current is represented by the letter i. The relationship between the voltage (V), resistance (R), and current (i or I) is V=IR; this is known as Ohm's law.
Common symbols	I
SI unit	ampere
Derivations from other quantities	${\displaystyle I={V \over R},I={Q \over t}}$
Dimension	${\displaystyle {\mathsf {I}}}$

In the International System of Units (SI), electric current is expressed in units of ampere (sometimes called an "amp", symbol A), which is equivalent to one coulomb per second. The ampere is an SI base unit and electric current is a base quantity in the International System of Quantities (ISQ). Electric current is also known as amperage and is measured using a device called an ammeter.

Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ordinary conductors, they cause Joule heating, which creates light in incandescent light bulbs. Time-varying currents emit electromagnetic waves, which are used in telecommunications to broadcast information.