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Reactance and Impedance: Explained with Difference and Importance
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Alternating Current
In Physics, the concept of alternating current is well discussed. While studying about alternating current, the terms reactance and impedance are more talked about rather than resistance in direct current. Both reactance and impedance are equivalent to that of resistance in its own way if the alternating current is considered.
In this article, you will learn and understand the concept of reactance and impedance along with their differences and importance.
Reactance and Impedance
Reactance and Impedance is equivalent to resistance in AC Circuit. These two provide opposition to the flow of alternating current in the circuit. Reactance and impedance are generated due to the presence of components like the capacitor and the inductor. They are generated due to electromotive force generated in these components.
What is Reactance?
Reactance is defined as the opposition in an AC circuit due to capacitance and inductance. It can be generated in the circuit due to two types of components which are the inductor and the capacitor.
The reactance of both types has the units of Ohms.
Inductive Reactance
If an inductor is placed in an AC circuit, the time-varying voltage of the circuit would result in a time-varying current in the circuit. Even if the inductor is made out of a material having negligible resistance the current in the circuit still decreases. This is because the inductor stores energy in the magnetic fields. The time-varying voltage results in a varying magnetic field. As the magnetic field changes around the inductor it creates an emf according to Faraday’s law of induction. According to Lenz law when an induced emf is caused due to changing magnetic field, a current flows in the direction which opposes the change. This is known as inductive reactance and is equivalent to the effect of resistance.
The formula for inductive resistance is
Where,
f = Frequency of the alternating current
L = Inductance of the inductor
Capacitive Reactance
The capacitive reactance is due to capacitors present in the AC circuit. When the capacitor gets gradually charged, the opposing electric field between the plates of the capacitor also increases. This opposing electric field gets so high that in fully charged conditions it completely cuts off the circuit.
The capacitive reactance is stated by the formula
Where,
f = Frequency of the alternating current
C = Capacitance of the inductor
What is Impedance?
The Impedance in a circuit can be defined as the resistance that the current and the voltage feels in an AC circuit. It is a combination of both resistance and reactance. It is mathematically stated as
Where,
Z = Impedance
R = Resistance in the circuit
It is represented in the units of Ohms.
Difference between Reactance and Impedance Reactance Impedance Reactance is the opposing force provided by individual components like inductor and capacitor. Impedance is the combination of the resistance and the reactance present in an AC circuit. Reactance can be of two types which are capacitive and inductive. Impedance can be broken down into resistance and reactance. Reactance is represented by the letter X Impedance is represented by the letter Z. Reactance is present in the circuit in the presence of either the capacitor or the inductor. Impedance is present in the circuit only when both capacitor and inductor are present or when capacitor, inductor, resistance are present. It is mathematically stated by formulas It is mathematically stated as
| Reactance | Impedance |
| Reactance is the opposing force provided by individual components like inductor and capacitor. | Impedance is the combination of the resistance and the reactance present in an AC circuit. |
| Reactance can be of two types which are capacitive and inductive. | Impedance can be broken down into resistance and reactance. |
| Reactance is represented by the letter X | Impedance is represented by the letter Z. |
| Reactance is present in the circuit in the presence of either the capacitor or the inductor. | Impedance is present in the circuit only when both capacitor and inductor are present or when capacitor, inductor, resistance are present. |
| It is mathematically stated by formulas | It is mathematically stated as |
Importance of Reactance and Inductance
The importance of inductance and resistance are:
Inductance and reactance result in slow growth of the current in the circuit rather than an instantaneous growth. Thus, it is used in the design of surge protection for AC circuits.
Hope this article about Reactance and Impedance was able to get the concept of this topic in motion. There are many such interesting topics and their real-life applications to learn about, just download the Testbook app and start browsing to get insights on them which can clear all your concepts regarding them.
Reactance and Impedance FAQs
What are reactance and impedance?
Reactance is defined as the opposition in AC Circuit due to capacitance and inductance.The Impedance in a circuit can be defined as the resistance that the current and the voltage feels in an AC circuit.
Can reactance be negative?
Yes, reactance can be negative.
What is the difference between reactance and impedance?
The difference between reactance and impedance is that reactance is due to any single component like an inductor or capacitor, whereas impedance is due to the resistance and reactance combined.
Are reactance and impedance the same?
No, reactance and impedance are not the same.
What is the S.I. unit of impedance?
The S.I. Unit of impedance is Ohms.
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