What is the difference between impedance and resistance?
Impedance is the effective resistance of a circuit containing reactive elements (capacitance and/or inductance) when an alternating EMF (voltage) is applied. It varies with the frequency of the applied voltage and is made up of: 1. Pure resistance (R) equivalent to the DC resistance of the circuit. 2. Capacitive reactance XC (which can be in series or parallel) 3, Inductive reactance XL (which can be either series or parallel) Impedance Z is a combination of R and XL or R and XC, and is written as R-jX or R+jX depending whether the final reactance is capacitive (leading current) or inductive (lagging current) So Z=R+jX or Z=R-jX where j represents an imaginary number (square root of -1) Resistance of a circuit is the “impedance” that a circuit shows to the application of a Direct Voltage (zero Hertz) and is given by the formula R=V/I where V is DC volts and I is DC Amps. Both impedance and resistance are expressed in ohms.
