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The ampere is an SI base unit and electric current is a base quantity in the International System of Quantities (ISQ). [4]: 15 Electric current is also known as amperage and is measured using a device called an ammeter. [2]: 788 Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers.
Skin effect — Tendency of charges to distribute at the surface of a conductor, when an alternating current passes through it. Static electricity — Class of phenomena involving the imbalanced charge present on an object, typically referring to charge with voltages of sufficient magnitude to produce visible attraction (e.g., static cling ...
In condensed matter physics and electrochemistry, drift current is the electric current, or movement of charge carriers, which is due to the applied electric field, often stated as the electromotive force over a given distance. When an electric field is applied across a semiconductor material, a current is produced due to the flow of charge ...
The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre, the vector direction of the field is the line of greatest slope of potential, and ...
The usual waveform of alternating current in most electric power circuits is a sine wave, whose positive half-period corresponds with positive direction of the current and vice versa (the full period is called a cycle). "Alternating current" most commonly refers to power distribution, but a wide range of other applications are technically ...
The term DC is used to refer to power systems that use only one electrical polarity of voltage or current, and to refer to the constant, zero-frequency, or slowly varying local mean value of a voltage or current. [9] For example, the voltage across a DC voltage source is constant as is the current through a direct current source.
Electric charges produce electric fields. [2] A moving charge also produces a magnetic field. [3] The interaction of electric charges with an electromagnetic field (a combination of an electric and a magnetic field) is the source of the electromagnetic (or Lorentz) force, [4] which is one of the four fundamental interactions in physics.
Ohm's law states that the electric current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, [1] one arrives at the three mathematical equations used to describe this relationship: [2]