# Impedance

Impedance, represented by the symbol $Z$, is **a measure of the opposition to electrical flow**. It is measured in ohms $\ohm$.

Resources

- Impedance by the Organic Chemistry Tutor

Difference between Resistance and Impedance?

Resistance is measured for DC circuits. Impedance is a more complex concept that includes resistance, but also the Reactance.

##### Khan Academy

I saw this Khan academy video where they use this formula, which is the norm of Impedance. $Z=R_{2}+(X_{L}−X_{C})_{2} $

In general, for $R$, $L$, and $C$ combinations, the impedance is defined to be the ratio between the Voltage Phasor $V$ and the Current Phasor $I$. $Z=IV $

#### Impedance of Resistance

$Z_{R}=R$ $V=Z_{R}I$

#### Impedance of Inductance

$Z_{L}=IV =jωL$ $V=Z_{L}I$

#### Impedance of Capacitance

$Z_{C}=IV =jωC1 =ωC−j $ $V=Z_{C}I$

### Rectangular Form

Another definition of Impedance is simply combining resistance $R$ and Reactance $X$ (which is defined for both $L$ and $C$) $Z=R+jX$

### Combinations of Impedance

These follow the same formula as for Resistor, but they are in terms of complex impedances instead of real resistance.

For **series** impedances, the formula is
$Z_{eq}=Z_{1}+Z_{2}+Z_{3}+…$

For **parallel** impedances, the formula is
$Z_{eq}1 =Z_{1}1 +Z_{2}1 +Z_{3}1 +…$