Difference between resistance and impedance

Difference between resistance and impedance
Difference between resistance and impedance

Resistance and impedance are the electrical properties that are present at the time material conduct electricity, both resistance and impedance are referred to as the electrical opposing property.

Definition for resistance and impedance 

Resistance is an opposing property experienced against the flow of current on a current-carrying conductor.

Impedance is also an opposing property, but it experiences only at AC circuits, a combination of capacitive, inductive, and resistance is combined and acts like impedance.

Frequency dependence at resistance and impedance

Theoretically, resistance is independent of the change in frequency, but at AC supplies, when the frequency increases, the movement of charges increases at the circuit, and as a result a property called skin effect is taken place and resistance will increase a little bit in theoretical perspective.

On the other hand, impedance is a property that is the combination of capacitive, inductive, and resistance properties.

At inductance, frequency is directly proportional to inductance

And frequency is inversely proportional to the capacitance    

Total resistance and total impedance

In a circuit, you can add resistance by applying ohm’s law, at a series circuit the total resistance is equal to the sum of all resistance.


At parallel circuit, it is 1/RT= 1/R1 + 1/R2 + 1/R3

So the total resistance at the parallel circuit is decreases compare to series.

The total impedance is not calculated arithmetically, because the capacitive and inductive reactance is included in the vector quantity, so the total impedance calculation is done vectorially.

Phase difference at resistance and impedance

In a perfect resistance material, the current is in-phase to voltage, the current flowing through the resistance is always proportional to voltage.

In an impedance material, a phase difference between voltage and current is present, the magnitude of the phase difference depends on the inductive and capacitive value.

Impedance and resistance is scalar or vector

Resistance is a scalar quantity because they only have magnitude but not direction.

Impedance is a vector quantity because it has magnitude and vector, the degree of rotation of phase is termed as vector.

Active or reactive power on resistance and impedance

Active or reactive power on resistance and impedance
Active or reactive power on resistance and impedance

The resistance consumes the active power and the impedance consumes reactive power due to the presence of capacitive and inductive properties.

The active power is the power dissipated at the circuit and resistance power consumes at the source and load of the circuit.

Impedance and resistance is in the real or imaginary part

The resistance is commonly calculated with real values such as 1ohm and 100ohm, but the impedance is laying in complex quantities, so they are calculated with real and imaginary parts.

Power dissipation due to resistance and impedance   

The resistance dissipates power in the form of heat, by converting the power into an electromagnetic field.

But at the same time impedance also dissipate power in the form of heat and at the same time the capacitive property at impedance store the energy.

Impedance and resistance depends on

Resistance of any material is independent of the current and voltage values, but it depends on the length of material, cross-section area, and temperature.

The impedance property depends on the frequency of the AC signal and phase angle.

How to measure impedance and resistance

The ohmmeter is used to measure the resistance at a circuit, but the impedance is measure with an impedance analyzer device, it is a complicated device that separately measures capacitance, resistance, and inductance.

Formula for impedance and resistance  

R is the alphabet used to indicate resistance and “Ω” is also used to indicate resistance value.

Z is the alphabet used to indicate impedance.

R= V/I Ω, this is the formula used to calculate resistance at a circuit.

Z= √R2 + (XL – XC) 2, this is the formula for calculating impedance.

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