Resistance is the opposition to the flow of current due to the material's properties. It is a real quantity measured in ohms (Ω).
Reactance is the opposition to the flow of current due to the storage of energy in electric and magnetic fields. It is an imaginary quantity also measured in ohms (Ω).
Impedance (Z) is the combination of resistance (R) and reactance (X) and can be represented as:
Z = R + jX
where:
* Z is the impedance
* R is the resistance
* X is the reactance
* j is the imaginary unit (√-1)
Key characteristics of impedance:
* Frequency-dependent: Impedance varies with the frequency of the AC signal.
* Phase-dependent: Impedance affects the phase relationship between voltage and current.
* Unit: Ohms (Ω)
Importance of impedance:
* Matching circuits: Impedances need to be matched for efficient power transfer in circuits.
* Filtering circuits: Impedances are used in filter circuits to selectively pass or block certain frequencies.
* Transmission lines: Impedance matching is crucial for minimizing signal loss and reflections in transmission lines.
Examples of impedance:
* Resistor: Impedance is equal to its resistance.
* Capacitor: Impedance decreases with increasing frequency.
* Inductor: Impedance increases with increasing frequency.
Note: In DC circuits, impedance is simply equal to resistance, as there is no reactance.