What is the total inductance when three inductors with values of 20 mH, 30 mH, and 40 mH are connected in series?

To determine the total inductance of inductors connected in series, the values of the individual inductors are simply added together. This principle arises from the fact that inductance behaves similarly to resistance in series circuits, leading to a straightforward summation of their individual values.

In this case, the three inductors have values of 20 mH, 30 mH, and 40 mH. Therefore, the total inductance can be calculated as follows:

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

This calculation confirms that when inductors are connected in series, their inductances do not simply combine in a unique or complex way; instead, they maintain a simple additive relationship resulting in a total of 90 mH. This is why the correct answer reflects the total sum of the individual inductance values.