Impedance is a concept related to AC whereas resistance is a concept related to DC. Their calculation of value is same which is R=V/I.

Difference Between Resistance and Impedance

Resistance is caused due to the electrons in a conductor colliding with the ionic lattice of the conductor which results in the conversion of electrical energy in heat. It could be said that electrical resistance is the opposition to steady electric current. An ideal resistance does change with frequency when connected with DC.

Impedance is the measure of the nature of opposition of the AC electricity which is created due to inductance and capacitance. This opposition varies with the frequency. Very often, reactance and impedance are thought to be the same and are interchangeably used. It is important to understand that reactance is the resistance offered to the AC current by inductors and capacitors only while impedance is the sum of the resistance and reactance.

Resistance

Impedance

It is used in DC circuits

It is used in AC circuits

Resistance can be seen in both AC and DC circuits

Impedance can be seen only in AC circuits

It happens due to resistive elements

It happens due to reactance and resistance

It is represented by letter R

It is represented by letter Z

It is represented using real numbers such as 5.3 ohms

It is represented using real and imaginary values such as R + ik

It does not vary depending upon the frequency of DC current

It varies according to the frequency of AC current.

It does not have a magnitude and phase angle

It does have a phase angle and magnitude

If kept in a electromagnetic field, it only shows the power dissipation

If kept in a electromagnetic field, it shows power dissipation and energy stored