Difference Between Impedance and Resistance

Resistance(R) can be defined as the measurement of the opposition which occurs in a flowing current in the electric circuit. Whereas, Impedance (Z) can be defined as the opposition present in the flowing current. Although both are measured using a resistor., there are some differences between them. The main difference between impedance and resistance is that resistance opposes the flow of both direct current (DC) and alternating current (AC), while Impedance solely opposes the flow of alternating current.

In this Physics article, we will look into the difference between impedance and resistance and their applications.

What is Impedance?

Impedance is defined as the measurement of the nature of opposition of the AC electricity which is produced by the inductance and capacitance. Impedance varies with the frequency of the current. Impedance consists of two parts: resistance and reactance. Impedance is measured in ohms, just like resistance, and it determines how much current can flow through a circuit when a voltage is applied.

What is Resistance?

Resistance occurs due to the presence of electrons in a conductor which collides with the ionic lattice present in the conductor and this phenomenon causes the conversion of electrical energy into heat. It is also said that electrical resistance is the opposition to a constant electric current. Materials with high resistance impede the flow of current more than materials with low resistance. Resistors are common components used to introduce a specific amount of resistance into a circuit. The higher the resistance, the lower the current that can flow through a circuit for a given voltage.

 

Difference Between Impedance and Resistance

Frequently, reactance and impedance are considered to be the same and are used interchangeably. But the reactance is the resistance offered to the AC electricity by inductors and capacitors only while impedance is the sum of all the three the resistance, inductor, and capacitor. In the table below are the mentioned differences between the impedance and the resistance:

Impedance	Resistance
It is used in AC circuits only.	It is used in DC circuits only.
It occurs due to resistive materials.	It occurs due to resistance, inductor, and the capacitor.
It is present only in the AC circuit.	It is present in both AC and DC circuits.
It is represented by ” Z”.	It is represented by “R”.
It does have a magnitude and a phase angle.	It does not have a magnitude and a phase angle.
It varies according to the frequency of the AC.	It does not vary according to the frequency of the DC.
It is depicted using real and imaginary values like .	It is depicted using real numbers like 4.8 ohms.
If it is kept in an electromagnetic field, it shows the dissipation of power and stored energy.	If it is kept in an electromagnetic field, it only shows the dissipation of power.

Below is the diagram showing impedance as well as resistance:

Applications of Impedance & Resistance

The applications of resistance are mentioned as follows:

• It is used in high-frequency instruments.
• It is also used in power control circuits.
• It is used in amplifiers.
• It is also used in oscillators.
• It is also used in telecommunication
• It is used like a digital multimeter.
• It is used in wave generators.
• It is also used in transmitters.
• It is also used in modulators.
• As well as it is used in demodulators.
• It is used in medical instruments.
• It is used in instrumentation applications.
• It is also used in voltage regulators.
• It is used in feedback amplifiers.
• It is also used in DC power supplies.
• These are also used in filter circuit networks.

The applications of impedance are mentioned as follows:

• It is used in capacitors to manage the flow of electric current, and capacitors are present in all electronic gadgets and devices.

Properties of Impedance and Resistance

The following are the properties of Impedance and Resistance: 

Magnitude

• For a resistor, in an impedance circuit. The magnitude of the resistor is the same for any voltage and frequency. 
• For inductors and capacitors, the magnitude of impedance is dependant on the frequency of the input sine wave.
• The magnitude of increases with the increase in frequency. 

• An inductor has a high impedance at a higher frequency.
• For a capacitor, the magnitude of decreases with an increase in the frequency. 

Phase

• Phase refers to the delay in between two sine waves. 
• For a linear LCR circuit, if the input voltage is a sine wave. It has also been observed that the output current voltage is also a sine wave.
• For a series of resistors, the voltage and current overlap. They are always in phase. The phase angle between current and voltage is 0°. 
• For inductors and capacitors, the voltage and current dont overlap. They are always out of phase by 90°. 

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