VARIATION OF CAPACITIVE REACTANCE WITH CAPACITANCE

Reactance:

In the analysis of an alternating-current electrical circuit (for example a RLC series circuit), reactance is the imaginary part of impedance, and is caused by the presence of inductors or capacitors in the circuit. Reactance produces a phase shift between the electric current and voltage in the circuit. Reactance is denoted by the symbol X and is measured in ohms.

• If X > 0, the reactance is said to be inductive.
• If X = 0, then the circuit is purely resistive, i.e. it has no reactance.
• If X < 0, it is said to be capacitive.

The relationship between impedance, resistance, and reactance is given by the equation

Z=  R + jX

where,

Z is impedance in ohms,

R is resistance in ohms,

X is reactance in ohms,

and j is the imaginary unit  √-1

Often it is enough to know the magnitude of the impedance:

    | Z | = √R² + X²

For a purely inductive or capacitive element, the magnitude of the impedance simplifies to just the reactance.

The reactance is given by

X = X_L - X_C

where X_L and X_C are the inductive and capacitive reactances, respectively.

Capacitive Reactance:

Capacitive reactance (symbol X_C) reflects the fact that electrons cannot pass through a capacitor, yet effectively alternating current (AC) can: the higher the frequency the better. There is also a phase difference between the alternating current flowing through a capacitor and the potential difference across the capacitor's electrodes.

Capacitive reactance has the formula

    X_C = 1/ωC = 1/ 2πfC

where

X_C is the capacitive reactance measured in ohms

ω is the angular frequency, measured in radians per second

f is the frequency, measured in hertz

C is the capacitance, measured in farads.