History and Definition of Ampere
– The ampere is named after French physicist and mathematician André-Marie Ampère.
– Ampère studied electromagnetism and laid the foundation of electrodynamics.
– An international convention in 1881 established the ampere as a standard unit of electrical measurement.
– The ampere was originally defined as one tenth of the unit of electric current in the centimetre–gram–second system.
– The international ampere was defined as the current that would deposit 0.001118 grams of silver per second.
– Until 2019, the SI defined the ampere as the current that would produce a force of 2×10 newtons per metre of length between two parallel conductors.
– Ampère’s force law states that there is an attractive or repulsive force between two parallel wires carrying an electric current.
– The coulomb, the SI unit of charge, was defined as the quantity of electricity carried in 1 second by a current of 1 ampere.
– The ampere was realized using a Kibble balance and maintained via Ohm’s law from the units of electromotive force and resistance.
– The 2019 redefinition of the SI base units defined the ampere by fixing the numerical value of the elementary charge.
– The elementary charge is 1.602176634×10^-19 coulombs.
– The SI unit of charge, the coulomb, is the quantity of electricity carried in 1 second by a current of 1 ampere.
– The ampere is defined in terms of the unperturbed ground state hyperfine transition frequency of the caesium-133 atom.
Units Derived from the Ampere
– The SI derived units derived from the ampere include the volt, ohm, watt, tesla, and weber.
– The volt is the unit of electromotive force or electric potential difference.
– The ohm is the unit of electrical resistance.
– The watt is the unit of power.
– The tesla is the unit of magnetic flux density, and the weber is the unit of magnetic flux.
SI Prefixes and Modification of Ampere
– The ampere can be modified by adding a prefix that multiplies it by a power of 10.
– Common SI prefixes used with the ampere include kilo-, mega-, micro-, and nano-.
– These prefixes indicate multiplication or division by factors of 10.
– For example, a kiloampere is 1000 amperes, and a microampere is one millionth of an ampere.
– SI prefixes are used to express current values in a more convenient and readable format.
Importance and Applications of Ampere
– The ampere is a crucial unit for measuring and quantifying electric current in various practical applications.
– It is used in electrical engineering to design and analyze circuits, determine power consumption, and ensure proper functioning of electrical devices.
– The ampere is essential in the field of electronics for measuring current flow in components such as resistors, capacitors, and transistors.
– It is also vital in power generation and distribution systems to monitor and control the flow of electricity.
– The accurate measurement and control of amperes are crucial for safety and efficiency in electrical systems.
Relationship with Other Units and Future Developments
– The ampere is closely related to other units in the International System of Units (SI).
– It is defined in terms of the coulomb, which is the SI unit of electric charge.
– The relationship between the ampere and the coulomb is given by the equation: 1 ampere = 1 coulomb per second.
– The ampere is also related to the volt and the ohm through Ohm’s Law.
– The ampere, along with other SI units, is subject to periodic redefinitions to ensure precision and accuracy in measurements.
– In 2019, the ampere was redefined in terms of the elementary charge.
– This redefinition allows for a more precise and stable definition of the ampere based on fundamental constants of nature.
– The redefined ampere will be realized using advanced measurement techniques and technologies. Source: https://en.wikipedia.org/wiki/Ampere
The ampere (/ˈæmpɛər/ AM-pair, US: /ˈæmpɪər/ AM-peer; symbol: A), often shortened to amp, is the unit of electric current in the International System of Units (SI). One ampere is equal to 1 coulomb (C) moving past a point in 1 second. It is named after French mathematician and physicist André-Marie Ampère (1775–1836), considered the father of electromagnetism along with Danish physicist Hans Christian Ørsted.
| ampere | |
|---|---|
 Demonstration model of a moving iron ammeter. As the current through the coil increases, the plunger is drawn further into the coil and the pointer deflects to the right. | |
| General information | |
| Unit system | SI |
| Unit of | electric current |
| Symbol | A |
| Named after | André-Marie Ampère |
As of the 2019 redefinition of the SI base units, the ampere is defined by fixing the elementary charge e to be exactly 1.602176634×10−19 C, which means an ampere is an electric current equivalent to 1019 elementary charges moving every 1.602176634 seconds or 6.241509074×1018 elementary charges moving in a second. Prior to the redefinition the ampere was defined as the current passing through two parallel wires 1 metre apart that produces a magnetic force of 2×10−7 newtons per metre.
The earlier CGS system has two units of current, one structured similar to the SI's and the other using Coulomb's law as a fundamental relationship, with the CGS unit of charge defined by measuring the force between two charged metal plates. The CGS unit of current is then defined as one unit of charge per second.
