FAA AMT (Aviation Maintenance Technician) Airframe Practice Exam

When using an ohmmeter to check the continuity of a generator field coil, the coil should?

1. Show infinite resistance

2. Show very low resistance if it is a series field coil

3. Not register on the ohmmeter

4. Show medium resistance

The correct answer is: Show very low resistance if it is a series field coil

When using an ohmmeter to check the continuity of a generator field coil, the coil should show very low resistance if it is a series field coil because the windings are continuous with few turns of heavy wire, so the resistance should be relatively low. This is compared to a shunt field coil, which typically has more turns of finer wire and would show higher resistance on an ohmmeter. Options A, C, and D are incorrect: A. Showing infinite resistance would indicate an open circuit, meaning there is a break in the continuity of the coil, which is not the expected behavior when testing a functional field coil. C. Not registering on the ohmmeter would suggest that there is no conductivity, which is also not the expected behavior for a properly functioning field coil. D. Showing medium resistance would be more indicative of a shunt field coil rather than a series field coil, as series field coils typically have very low resistance due to their design.