|
The resistor, the
capacitor and the coil
all oppose the flow of
ac current.
Their combined
opposition is called
impedance, Z.
Ohm's Law can be
applied, as shown in the
top formula.
The higher the
impedance, the lower the
current.
The resistor has
resistance.
The capacitor has
capacitive reactance.
The coil has inductive
reactance.
All of these values are
measured in ohms.
However, impedance is
not calculated by adding
these values.
The bottom formula must
be used.
If you are familiar with
Pythagoras, this is
another application of
it.
When coupling one device
to another, such as an
amplifier to a
loudspeaker, the output
impedance of the
amplifier and the input
impedance of the speaker
must be the same, to
give optimum transfer of
power from one to the
other.
|
