What is the relation between reactance resistance and impedance?

The relationship between reactance, resistance, and impedance

1. Resistance

Resistance is a hindrance to the flow of current in the circuit, which only considers the resistance properties in the AC circuit. The unit of resistance is ohm (Ω), and its calculation formula is as follows:

R= V/I

V is for voltage

I is for current

Resistance is present in both DC and AC circuits, but in AC circuits it is only part of the impedance.3

2. Reactance

Reactance is the obstruction effect caused by alternating current in a circuit, which is divided into inductive reactance and capacitive reactance. Reactance exists only in AC circuits because it is related to the rate of change of current. The unit of reactance is also ohms (Ω).

Induced reactance (XL) : The obstruction caused by inductance, the formula is:

XL = 2 PI fL

f is for frequency

L is the inductance value

Capacitive reactance (XC) : The blocking effect caused by capacitance, the formula is:

XC=1/ (2πfC)

f is for frequency

C is the capacitance value

3. Impedance

Impedance is the total obstruction of the circuit to the alternating current, which includes the combined effect of resistance and reactance. Impedance is a complex number, expressed as:

Z=R+jX

R is for resistance

X is reactance

j is an imaginary unit.

The unit of impedance is also ohm (Ω). Impedance takes into account not only the resistance in the circuit, but also the influence of inductance and capacitance, so in AC circuits, the impedance is usually greater than the simple resistance 12.

Sum up

• Resistance: Considering only the obstructing effect of current flow, suitable for DC and AC circuits.

• Reactance: present only in AC circuits, including inductive and capacitive reactance, caused by inductance and capacitance, respectively.

• Impedance: a combination of resistance and reactance effects, suitable for AC circuits, indicating the total obstruction of the circuit to AC.

It can be seen from the above relationship that impedance is the combined performance of resistance and reactance in an AC circuit, while reactance is the specific effect caused by inductance and capacitance. Understanding these three concepts and their relationships is essential for the analysis and design of AC circuits.