Impedance

Impedance, abbreviated as Z, is a concept commonly used in the field of electrical engineering, electronics, and physics.  It refers to the opposition that a circuit presents to the flow of alternating current (AC).

In a simple circuit with just a resistor, impedance is equivalent to resistance (R).  However, in circuits with capacitors and inductors, impedance becomes a complex quantity because it involves both resistance and reactance.  Reactance is the opposition that a circuit element presents to the flow of alternating current due to its capacitance (in the case of capacitors) or inductance (in the case of inductors).

Impedance is measured in ohms.  It plays a role in analyzing and designing electrical circuits, especially in AC circuits where the relationship between voltage and current is more complex than in DC circuits.  Impedance matching is an important consideration in the design of electronic systems to optimize power transfer between components.

 

Impedance formula
\( Z \;=\; \sqrt{R^2 + ( X_l - X_c )^2 }  \)
Symbol	English	Metric
\( Z \) = impedance	\(\Omega\)	\(kg-m^2\;/\;s^3-A^2\)
\( X_c \) = capacitive resistance	\(\Omega\)	\(kg-m^2\;/\;s^3-A^2\)
\( X_l \) = inductive resistance	\(\Omega\)	\(kg-m^2\;/\;s^3-A^2\)
\( R \) = resistance	\(\Omega\)	\(kg-m^2\;/\;s^3-A^2\)