AC1 Fundamentals Unit 4 – Inductive Reactance
The total opposition to current flow in a circuit containing resistance (resistors) and inductive
reactance (inductors) is known as impedance (Z) and is measured in ohms.
You cannot directly add resistance (R) and inductive reactance (XL) to obtain the impedance
value (Z).
In a series circuit with resistance and inductive reactance, impedance (Z) is determined from the
following formula.
Z = √ R^2 + XL^2
A more practical approach to finding the impedance (Z) of XL and R in series is to divide the
total circuit current (IT) into the applied voltage (Vac).
Vac
Z =
IT
In a parallel circuit with resistance and inductive reactance, Z is determined from the following
formula.
R x XL
Z =
√ R^2 +XL^2
Again, a more practical approach to finding the impedance (Z) of XL and R in parallel is to
divide the total circuit current (IT) into the applied voltage (Vac).
Vac
Z =
IT