# ampere

(noun)

## Definition of ampere

A unit of electrical current; the standard base unit in the International System of Units. Abbreviation: amp. Symbol: A.

Source: Wiktionary - CC BY-SA 3.0

## Examples of ampere in the following topics:

• ### Magnetic Force Between Two Parallel Conductors

• If the currents are in opposite directions, the force repels the wires.The force between current-carrying wires is used as part of the operational definition of the ampere.
• For parallel wires placed one meter away from one another, each carrying one ampere, the force per meter is:$\frac {F}{l}=\frac{(4\pi × 10^{-7} T \cdot m/A)(1A)^2}{(2\pi )(1m)}=2 ×10^{-7}N/m$The final units come from replacing T with 1N/(A×m).Incidentally, this value is the basis of the operational definition of the ampere.
• This means that one ampere of current through two infinitely long parallel conductors (separated by one meter in empty space and free of any other magnetic fields) causes a force of 2×10-7 N/m on each conductor.
• ### Overview

•  The SI unit for current is the ampere (A), named for the French physicist André-Marie Ampère (1775–1836).
• Since I=ΔQ/Δt, we see that an ampere is one coulomb per second:$1 \ A = 1 \ C/s$The flow of electricity requires a medium in which charge can flow .
• ### Parallel-Plate Capacitor

• In practice, dielectrics do not act as perfect insulators, and permit a small amount of leakage current to pass through them.Capacitors are limited in their ability to prevent charge flow from one conductive surface to the other; their ability to hold charge is measured in Farads (F), which are defined as 1 ampere-second per volt, one joule per square volt and one Coulomb per volt, among other ways.For a parallel-plate capacitor, capacitance (C) is related to dielectric permittivity (ε), surface area (A), and separation between the plates (d):$C=\frac {\epsilon A}{d}$Voltage (V) of a capacitor is related to distance between the plates, dielectric permittivity, conductor surface area, and charge (Q) on the plates:$V= \frac {Qd}{\epsilon A}$Depending on the dielectric strength (Eds) and distance (d) between plates, a capacitor will "break" at a certain voltage (Vbd).
• ### Energy Stored in a Magnetic Field

• The formula for this energy is given as: $E = \frac{1}{2} LI^2$(Eq. 1), where L is the inductance in units of Henry and I is the current in units of Ampere.
• ### Applications

• We now must solve this equation for each of the three unknown variables, which will require three different equations.Considering loop abcdea, we can use Kirchhoff's loop rule:$-I_2R_2+ \mathrm{emf}_1-I_2r_1-I_1R_1=-I_2(R_2)+r_1)+\mathrm{emf}_1-I_1R_1=0$Substituting values of resistance and emf from the figure diagram and canceling the ampere unit gives:$-3I_2+18-6I_1=0$This is the second part of a system of three equations that we can use to find all three current values.