Resistance vs Impedance-difference between Resistance and Impedance

This page on Resistance vs Impedance describes basic difference between Resistance and Impedance.

Following table mentions comparison between resistance and impedance terms.

Resistance Impedance
It is the opposition to flow of DC current. It is the opposition to flow of AC current.
It is measured in Ohm. It is also measured in Ohm.
It is measured by Ohm meter or multimeter. It is measured by Impedance meter.
Denoted by 'R' in the circuit. Denoted by 'Z' in the circuit. Where in, Z = R + jX (cartesian form), Z = |Z|ej*arg(z) (polar form)
Inverse of R is known as conductance(G), G=1/R. Inverse of Z is known as admittance(Y), Y =1/Z.
It does not depend on frequency. Resistance of material varies with temperature.
R =V/I as per Ohm's Law
Impedance depends on Frequency,
Z = R, Phase angle=0
Z = XL=W*L, Phase angle=90
Z= XC=1/W*C, Phase angle=-90
For R-L Circuit, Z = { R2 + (XL)2 }0.5..0 degree<f<90 degree
For R-C Circuit, Z = { R2 + (XC)2 }0.5.-90 degree<f<0 degree
For R-L-C circuit, Z = [ R2 + {(XL)-(XL)}2 ]0.5


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