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.