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An ampere-hour or amp-hour (symbol: A⋅h or A h; often simplified as Ah) is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour, or 3,600 coulombs. [1] [2]
The ampere is named for French physicist and mathematician André-Marie Ampère (1775–1836), who studied electromagnetism and laid the foundation of electrodynamics.In recognition of Ampère's contributions to the creation of modern electrical science, an international convention, signed at the 1881 International Exposition of Electricity, established the ampere as a standard unit of ...
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.
The volt-ampere (SI symbol: VA, [1] sometimes V⋅A or V A) is the unit of measurement for apparent power in an electrical circuit. It is the product of the root mean square voltage (in volts) and the root mean square current (in amperes). [2] Volt-amperes are usually used for analyzing alternating current (AC) circuits.
The henry (symbol: H) is the unit of electrical inductance in the International System of Units (SI). [1] If a current of 1 ampere flowing through a coil produces flux linkage of 1 weber turn, that coil has a self-inductance of 1 henry. The unit is named after Joseph Henry (1797–1878), the American scientist who discovered electromagnetic induction independently of and at about the same ...
where is the armature current of the machine (SI unit: ampere). is primarily used to calculate the armature current for a given torque demand: = The SI units for the torque constant are newton meters per ampere (N·m/A).
Factor () Value Item 10 −19: 160 zA Current flow of one electron per second : 10 −12: 1-15 pA Range of currents associated with single ion channels [calcium (1 pA), sodium (10-14 pA), potassium (6 pA)] as measured by patch-clamp studies of biological membranes
The drift velocity in a 2 mm diameter copper wire in 1 ampere current is approximately 8 cm per hour. AC voltages cause no net movement. The electrons oscillate back and forth in response to the alternating electric field, over a distance of a few micrometers – see example calculation.