If three coils in a series circuit each have an inductance of 0.3 henrys, what is the total inductance at a frequency of 60 Hz?

To determine the total inductance of multiple inductors connected in series, you simply sum their inductance values. In this scenario, you have three coils, each with an inductance of 0.3 henrys. The total inductance is calculated as follows:

Total inductance = Inductance of coil 1 + Inductance of coil 2 + Inductance of coil 3

Total inductance = 0.3 H + 0.3 H + 0.3 H = 0.9 H

Therefore, for the series connection of three coils, the total inductance is 0.9 henrys. The frequency of the circuit, in this case, 60 Hz, does not affect the calculation of the total inductance because inductance is independent of frequency.

This is why the selection of 0.9 henrys is the correct answer in this context.