The coil opposes the flow of ac current, as a resistor does in a dc circuit.
This
opposition
is
called
inductive
reactance,
**XL**. It is measured in ohms. Ohm's Law can be applied, as in the top formula.
The
bottom
formula
shows
how
inductive
reactance
is
calculated.
f is the frequency of the applied voltage, and L is the value of the coil in Henries.
It can be seen from this formula that the value of
**XL** goes up as the frequency increases. It also goes up if the value of the coil increases.
This means that as the value of L or f increases, the opposition to the flow of ac
current
increases,
and the
lamp
will
glow
less. |