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# Electrical reactance

In electrical and electronic systems, reactance is the opposition of a circuit element to a change in current or voltage, due to that element's inductance or capacitance. 

Addison-Wesley is a publisher of textbooks and computer literature.

## Alternating current

Alternating current (AC) is an electric current which periodically reverses direction, in contrast to direct current (DC) which flows only in one direction.

## Amplitude

The amplitude of a periodic variable is a measure of its change over a single period (such as time or spatial period).

## Angular frequency

In physics, angular frequency ω (also referred to by the terms angular speed, radial frequency, circular frequency, orbital frequency, radian frequency, and pulsatance) is a scalar measure of rotation rate.

## Capacitance

Capacitance is the ratio of the change in an electric charge in a system to the corresponding change in its electric potential.

## Capacitor

A capacitor is a passive two-terminal electrical component that stores potential energy in an electric field.

## Dielectric

A dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field.

## Direct current

Direct current (DC) is the unidirectional flow of electric charge.

## Electric charge

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field.

## Electric current

An electric current is a flow of electric charge.

## Electric field

An electric field is a vector field surrounding an electric charge that exerts force on other charges, attracting or repelling them.

## Electrical impedance

Electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied.

## Electrical resistance and conductance

The electrical resistance of an electrical conductor is a measure of the difficulty to pass an electric current through that conductor.

## Electrical resistivity and conductivity

Electrical resistivity (also known as resistivity, specific electrical resistance, or volume resistivity) is a fundamental property that quantifies how strongly a given material opposes the flow of electric current.

## Electromagnetic coil

An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil, spiral or helix.

## Electromotive force

Electromotive force, abbreviated emf (denoted \mathcal and measured in volts), is the electrical intensity or "pressure" developed by a source of electrical energy such as a battery or generator.

Faraday's law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)—a phenomenon called electromagnetic induction.

## Frequency

Frequency is the number of occurrences of a repeating event per unit of time.

## Gyrator–capacitor model

The gyrator–capacitor model is a lumped-element model for magnetic fields, similar to magnetic circuits, but based on using elements analogous to capacitors (see magnetic capacitance) rather than elements analogous to resistors (see magnetic reluctance) to represent the magnetic flux path.

## Harmonic

A harmonic is any member of the harmonic series, a divergent infinite series.

## Imaginary unit

The imaginary unit or unit imaginary number is a solution to the quadratic equation.

## Inductance

In electromagnetism and electronics, inductance is the property of an electrical conductor by which a change in electric current through it induces an electromotive force (voltage) in the conductor.

## Inductor

An inductor, also called a coil, choke or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it.

## Insulator (electricity)

An electrical insulator is a material whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field.

## Magnetic field

A magnetic field is a vector field that describes the magnetic influence of electrical currents and magnetized materials.

## Ohm

The ohm (symbol: Ω) is the SI derived unit of electrical resistance, named after German physicist Georg Simon Ohm.

## Phasor

In physics and engineering, a phasor (a portmanteau of phase vector), is a complex number representing a sinusoidal function whose amplitude (A), angular frequency (ω), and initial phase (θ) are time-invariant.

## Potential

Potential generally refers to a currently unrealized ability.

## Proportionality (mathematics)

In mathematics, two variables are proportional if there is always a constant ratio between them.

## Resistor

A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element.

## San Francisco

San Francisco (initials SF;, Spanish for 'Saint Francis'), officially the City and County of San Francisco, is the cultural, commercial, and financial center of Northern California.

## Short circuit

A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or a very low electrical impedance.

## Sine wave

A sine wave or sinusoid is a mathematical curve that describes a smooth periodic oscillation.

## Square wave

A square wave is a non-sinusoidal periodic waveform in which the amplitude alternates at a steady frequency between fixed minimum and maximum values, with the same duration at minimum and maximum.

## Susceptance

In electrical engineering, susceptance (B) is the imaginary part of admittance, where the real part is conductance.

## The Art of Electronics

The Art of Electronics, by Paul Horowitz and Winfield Hill, is a popular textbook dealing with analog and digital electronics.

## Voltage

Voltage, electric potential difference, electric pressure or electric tension (formally denoted or, but more often simply as V or U, for instance in the context of Ohm's or Kirchhoff's circuit laws) is the difference in electric potential between two points.

## References

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