Impedance, denoted Z, is an expression of the opposition that an electronic component, circuit, or system offers to alternating and/or direct electric current.Impedance is a vector (two-dimensional)quantity consisting of two independent scalar (one-dimensional) phenomena: resistance and reactance.
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Answered by Nishu's , an ibibo Master, at 5:21 PM on October 12, 2008

Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current (AC). Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative amplitudes of the voltage and current, but also the relative phases. Impedance is a complex quantity and the term complex impedance may be used interchangeably; the polar form conveniently captures both magnitude and phase characteristics,


where the magnitude represents the ratio of the voltage difference amplitude to the current amplitude, while the argument gives the phase difference between voltage and current. In Cartesian form,


where the real part of impedance is the resistance and the imaginary part is the reactance . Dimensionally, impedance is the same as resistance; the SI unit is the ohm. The term impedance was coined by Oliver Heaviside in July 1886.

The reciprocal of impedance is admittance.

Answered by BAGYALAKSHMI , an ibibo Advisor, at 12:52 PM on October 12, 2008

Impedance is the total opposition a cable offers to alternating current. It includes both resistance and reactance and is generally expressed in Ohms

Answered by Reeta K , an ibibo Master, at 12:27 AM on October 12, 2008

Hi Anuj

I guess you want to know about impedance.

Well, Impedance is a measure of the impediment to the flow of alternating current at a given frequency. Larger numbers mean higher resistance to current flow. Impedance is a combination of resistance and reactance. The practical difference between impedance and resistance is that impedance changes as a function of frequency. Impedance is measured in "ohms", denoted by the letter "Z."

Thanks n regards

Suparn@

Answered by Suparna , an ibibo Master, at 9:01 PM on October 11, 2008

In electrical engineering, impedance measures how easily a circuit conducts current when a voltage runs through it. Measured in ohms, impedance is a way of telling you how much of the voltage introduced at one end will really make it to the other end. Impedance depends on other qualities of electricity, such as resistance, reactance, inductance, and capacitance.

Answered by Kamlesh B , an ibibo Specialist, at 6:26 PM on October 11, 2008

Well Anuj , Impedance is a concept associated with the transmission of waves and electrical signals. There are many kinds of waves, and impedance is different in each of them, hence this disambiguation page. However, impedance is also a unifying concept. It is related to the load that is imposed on the source that generates a wave.

It governs the reflection and transmission of waves incident on a change of medium. If the impedances in the two media match, there will be no reflection. One simple approach identifies two parameters for a wave: the restoring force that tries to return to equilibrium and the inertia of the medium displaced. Then the impedance is

Z = the square root of (restoring force) times (inertia)

while the velocity of the wave is

v = the square root of (restoring force) divided by (inertia)

For example, for a sound wave the restoring force is the modulus of elasticity, while the inertia is just the density. For some waves (light waves, for example) it is not obvious how this simple picture for mechanical waves can be applied, but the same general picture holds.


Impedance may refer to:

* the ratio of the voltage phasor to the electric current phasor, as in
o Electrical impedance, a measure of opposition to time-varying electric current in an electric circuit.
o Characteristic impedance, a measure of opposition to electric current propagation in a transmission line.
* Impedance matching and Impedance mismatch.
* Vacuum impedance, a universal constant.
* Electromagnetic impedance, a constant related to electromagnetic wave propagation in a medium.
* Mechanical impedance, a measure of opposition to motion of a structure subjected to a force.
* Acoustic impedance, a constant related to the propagation of sound waves in an acoustic medium.
* Linear response function, a general way to represent the input-output characteristics of a system.
* Object-relational impedance mismatch, difficulties encountered when a relational database management system is in an object-oriented programming language.


For more details , Please visit the source site :

http://en.wikipedia.org/wiki/I mpedance

Answered by Alok Gupta , an ibibo Guru, at 6:07 PM on October 11, 2008