Search results
Results from the WOW.Com Content Network
This definition of the ampere was most accurately realised using a Kibble balance, but in practice the unit was maintained via Ohm's law from the units of electromotive force and resistance, the volt and the ohm, since the latter two could be tied to physical phenomena that are relatively easy to reproduce, the Josephson effect and the quantum ...
Current density is the rate at which charge passes through a chosen unit area. [25]: 31 It is defined as a vector whose magnitude is the current per unit cross-sectional area. [2]: 749 As discussed in Reference direction, the direction is arbitrary. Conventionally, if the moving charges are positive, then the current density has the same sign ...
electric current: ampere (A) moment of inertia: kilogram meter squared (kg⋅m 2) intensity: watt per square meter (W/m 2) imaginary unit: unitless electric current: ampere (A) ^ Cartesian x-axis basis unit vector unitless current density: ampere per square meter (A/m 2) impulse
Contrast direct current. ammeter An instrument that is used to measure electric current. amorphous solid A type of solid which does not have a definite geometric shape. ampere (A) Often abbreviated as amp. The SI base unit of electric current, defined as one coulomb of electric charge per second. amplifier. Also electronic amplifier or ...
Unit name Symbol Base units E energy: joule: J = C⋅V = W⋅s kg⋅m 2 ⋅s −2: Q electric charge: coulomb: C A⋅s I electric current: ampere: A = C/s = W/V A J electric current density: ampere per square metre A/m 2: A⋅m −2: U, ΔV; Δϕ; E, ξ potential difference; voltage; electromotive force: volt: V = J/C kg⋅m 2 ⋅s −3 ⋅A ...
where E is the electric field vector with units of volts per meter (analogous to V of Ohm's law which has units of volts), J is the current density vector with units of amperes per unit area (analogous to I of Ohm's law which has units of amperes), and ρ "rho" is the resistivity with units of ohm·meters (analogous to R of Ohm's law which has ...
All other electric and magnetic units are derived from these four base units using the most basic common definitions: for example, electric charge q is defined as current I multiplied by time t, =, resulting in the unit of electric charge, the coulomb (C), being defined as 1 C = 1 A⋅s.
The SI system after 1983, but before the 2019 revision: Dependence of base unit definitions on other base units (for example, the metre is defined as the distance travelled by light in a specific fraction of a second), with the constants of nature and artefacts used to define them (such as the mass of the IPK for the kilogram).