In the analysis of an electrical circuit to alternating current the reactance is the imaginary part of the impedance and is

caused by the presence of inductors and / or capacitors in the circuit. The ballast produces a phase difference between the current and

the voltage of the circuit. Ballast is symbolized by the letter X and is measured in

ohms.

In electrical impedance is a physical quantity vector which represents the

strength of the opposition of a circuit to the passage of an alternating electric

currentCommonly the impedance is indicated with Z and its unit of measurement is the

ohm. / The concept of impedance generalizes Ohm's law extending it to the circuits

operating in sinusoidal (commonly said alternating current): under the current

represents the electrical resistance.