What is the total inductance when three series inductors have values of 20 mH, 30 mH, and 40 mH respectively?

In a series circuit, the total inductance is calculated by simply adding the individual inductances together. This is because in a series configuration, the magnetic fields of the inductors combine, resulting in a total inductance that is the sum of their values.

For the given inductors with values of 20 mH, 30 mH, and 40 mH, you would perform the calculation as follows:

Total Inductance = 20 mH + 30 mH + 40 mH = 90 mH.

Therefore, the total inductance of the three inductors connected in series amounts to 90 mH, making that the correct answer. This principle is essential in understanding how inductive components work together in electrical circuits.