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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.
In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. [1] The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.
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 ...
Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The electric current produces a magnetic field around the conductor. The magnetic field strength depends on the magnitude of the electric current, and therefore follows any changes in the magnitude of the current.
The red dot e 1 shows a conduction electron in the sheet right after it has undergone a collision with an atom, and e 2 shows the same electron after it has been accelerated by the magnetic field. On average at e 1 the electron has the same velocity as the sheet (v, black arrow) in the +x direction.
Charge is quantized: it comes in integer multiples of individual small units called the elementary charge, e, about 1.602 × 10 −19 C, [1] which is the smallest charge that can exist freely. Particles called quarks have smaller charges, multiples of 1 / 3 e , but they are found only combined in particles that have a charge that is an ...
William Sturgeon built an electric motor in 1832 and invented the commutator, a ring of metal-bristled brushes which allow the spinning armature to maintain contact with the electric current and changed the alternating current to a pulsating direct current. He also improved the voltaic battery and worked on the theory of thermoelectricity.
Galvanism is a term invented by the late 18th-century physicist and chemist Alessandro Volta to refer to the generation of electric current by chemical action. [2] The term also came to refer to the discoveries of its namesake, Luigi Galvani , specifically the generation of electric current within biological organisms and the contraction ...