Impedance

The ratio of a sinusoidal voltage to a sinusoidal current is called "impedance". This is a generalization of Ohm's Law for resistors. We derive the impedance of a resistor, inductor, and capacitor. The inductor and capacitor impedance includes a term for frequency, so the impedance of these components depends on frequency. Created by Willy McAllister. Sorry for the confusion. The value e^jwt can be assigned to anything, just like any other number, like 3 or -9. If I say, "Let v = 3," there is an understood unit of volts based on the context of the equation. It would be better if I said "Let v = 3 V," but I left that part out in the video. Later on, I might starting talking about current, and I could say, "Let i = 3". Again, I neglected to state the units, which is not the greatest teaching technique, but it is a good bet I'm assuming the units are amperes. In these two examples with "3", where I didn't state the units, you probably wouldn't think that 3 volts = 3 ampere. The same thing is happening in the video when I write I = e^jwt and then U (voltage) = e^jwt. The e^jwt is just a numerical function (that happens to be a function of time). Stated by itself, e^jwt does not have units, just like "3" doesn't have units. e^jwt becomes a value with units from the context of the equation where its used. Let me know if that helped answer your question. We substitute e^(jwt) for the current instead of the cosine function, to figure out impedance, and I get that but I don't under...

Impedance is the opposition of a circuit to alternating current. It's measured in ohms. To calculate impedance, you must know the value of all resistors and the impedance of all inductors and capacitors, which offer varying amounts of opposition to the current depending on how the current is changing in strength, speed, and direction. You can calculate impedance using a simple mathematical formula. • Impedance Z = R or X L or X C (if only one is present) • Impedance in series only Z = √(R 2 + X 2) (if both R and one type of X are present) • Impedance in series only Z = √(R 2 + (|X L - X C|) 2) (if R, X L, and X C are all present) • Impedance in any circuit = R + jX (j is the imaginary number √(-1)) • Resistance R = ΔV / I • Inductive reactance X L = 2πƒL = ωL • Capacative reactance X C = 1 / 2πƒC = 1 / ωC Define impedance. Impedance is represented with the symbol Z and measured in Ohms (Ω). You can measure the impedance of any X Research source • Resistance (R) is the slowing of current due to effects of the material and shape of the component. This effect is largest in resistors, but all components have at least a little resistance. • Reactance (X) is the slowing of current due to electric and magnetic fields opposing changes in the current or voltage. This is most significant for inductors. Review resistance. Resistance is a fundamental concept in the study of electricity. You'll see it most often in Ohm's law: ΔV = I * R. X Research source R = ΔV / I. You can also • ΔV ...

What is Impedance? Impedance is the amount of resistance that a component offers to current flow in a circuit at a specific frequency. In this article, we'll talk about how impedance is similar to and how it differs from just plain resistance. First, we'll not the similarities of the two. Impedance, just like resistance, is a value which show the amount of resistance that a component has to the flow of electrical current. And just like resistance, the unit to measure impedance is ohms(Ω). However, unlike resistance, impedance differs in that the amount of resistance that a component has to a signal varies with the signal's frequency. This means that the resistance of the component varies depending on the frequency of the signal entering the component. Resistance is a value and measure which is independent of frequency. It doesn't take into account the frequency of the signal passing through it, because frequency doesn't affect the resistance of nonreactive components. However, reactive components (which we'll discuss below) change the amount of resistance they offer in a circuit depending on the input signal's frequency. But impedance varies according to the frequency of the signal entering it. This is the difference between resistance and impedance. So the next step question to answer is, which components are affected by frequency and offer different resistances based on frequency and which components do not change according to the frequency entering in? And the answer is...

By • What is impedance? Impedance, denoted Z, is an expression of the opposition that an electronic component, circuit, or system offers to alternating and/or direct electric Resistance, denoted R, is a measure of the extent to which a substance opposes the movement of electrons among its Reactance, denoted X, is an expression of the extent to which an electronic component, circuit, or system stores and releases energy as the current and voltage fluctuate with each AC cycle. Reactance is expressed in imaginary number ohms. It is observed for AC, but not for DC. When AC passes through a component that contains reactance, energy might be stored and released in the form of a magnetic field, in which case the reactance is inductive (denoted + jX L); or energy might be stored and released in the form of an electric field, in which case the reactance is capacitive (denoted - jX C). Reactance is conventionally multiplied by the positive square root of -1, which is the unit imaginary number called the j operator, to express Z as a complex number of the form R + jX L (when the net reactance is inductive) or R - jX C (when the net reactance is capacitive). The illustration shows a coordinate plane modified to denote complex-number impedances. Resistance appears on the horizontal axis, moving toward the right.(The left-hand half of this coordinate plane is not normally used because negative resistances are not encountered in common practice.)Inductive reactance appears on the positiv...

Recent Examples on the Web Its thick front panel features three headphone outputs—6.3 mm, 4.4 mm and four-pin XLR—and offers adjustable impedance matching for fine-tuning. — Robert Ross, Robb Report, 13 Dec. 2022 When these switches in the new device are triggered at the same time, the impedance of the strip doubles in about 3 nanoseconds. — IEEE Spectrum, 21 Mar. 2023 This allowed the researchers to trigger the switches at will, doubling impedance along the strip. — Darren Orf, Popular Mechanics, 15 Mar. 2023 The low impedance of the capacitor minimizes any remaining ripple voltage on the battery side. — IEEE Spectrum, 10 Jan. 2023 Enlarge / The Galaxy Watch 5 uses bioelectrical impedance analysis to measure body composition in less than 15 seconds. — Corey Gaskin, Ars Technica, 15 Feb. 2023 Medical-grade scales that offer bioelectric impedance are more accurate in assessing body composition than home scales. — Caroline Thomason, Health, 6 Feb. 2023 Most earbuds or headphones with an impedance of 16Ω will work fine with the Rhodium. — Mark Sparrow, Forbes, 10 July 2022 Demonstrates head tracking, stereo vision, fine manipulation, bimanual manipulation, safe impedance control, and navigation. — IEEE Spectrum, 20 Jan. 2023 See More These examples are programmatically compiled from various online sources to illustrate current usage of the word 'impedance.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors.

A circuit where the current lags 90° (electrical) in respect of the applied voltage in a purely inductive circuit. A circuit where current leads 90° (electrical) in respect of the applied voltage in a purely capacitive circuit. A circuit where the current does not lag nor lead in respect to the applied voltage in a purely resistive circuit. When a circuit is driven with In a practical circuit where both In the AC circuit, the cumulative effect of reactance and impedance. The impedance is normally denoted by English letter Z. The value of impedance is represented as Where R is the value of circuit resistance and X is the value of circuit reactance. The angle between applied voltage and current is The inductive reactance is taken as positive and capacitive reactance is taken as negative. Impedance can be represented in complex form. This is The real part of a complex impedance is resistance and the imaginary part is reactance of the circuit. Let us apply a sinusoidal voltage Vsinωt across a pure The expression of current through the inductor is From the expression of the waveform of the current through the inductor it is clear that the current lags the applied voltage by 90° (electrical). Now let us apply same sinusoidal voltage Vsinωt across a pure The expression of current through the capacitor is From the expression of the waveform of the current through the capacitor it is clear that the current leads the applied voltage by 90°(electrical). Now we will connect the same v...

Before we begin to explore the effects of Resistance This is essentially friction against the flow of current. It is present in all conductors to some extent (except superconductors!), most notably in resistors. When the alternating current goes through a Reactance This is essentially inertia against the flow of current. It is present anywhere electric or magnetic fields are developed in proportion to an applied voltage or current, respectively; but most notably in capacitors and inductors. When the alternating current goes through a pure reactance, a voltage drop is produced that is 90° out of phase with the current. Reactance is mathematically symbolized by the letter “X” and is measured in the unit of ohms (Ω). Impedance This is a comprehensive expression of any and all forms of opposition to current flow, including both resistance and reactance. It is present in all circuits, and in all components. When the alternating current goes through an impedance, a voltage drop is produced that is somewhere between 0° and 90° out of phase with the current. Impedance is mathematically symbolized by the letter “Z” and is measured in the unit of ohms (Ω), in complex form. Perfect resistors possess resistance, but not reactance. Perfect inductors and perfect capacitors possess reactance but no resistance. All components possess impedance, and because of this universal quality, it makes sense to translate all component values (resistance, inductance, capacitance) into common terms of...