The correct answer is: C. fixed coils
The Weston synchronoscope is a device used to synchronize two alternating current (AC) generators. It consists of a moving coil and two fixed coils, which are connected to the generators. The moving coil is suspended in the magnetic field of the fixed coils, and its deflection indicates the phase difference between the two generators.
When the two generators are in phase, the moving coil is not deflected. As the phase difference increases, the moving coil deflects to the right. When the phase difference is 180 degrees, the moving coil is deflected to the left.
The Weston synchronoscope is a very accurate device, and it is used in a variety of applications, including power generation, power transmission, and power distribution.
The other options are incorrect because:
- Option A: The bus-bars are the conductors that connect the generators to the power system. The moving coil is not connected to the bus-bars.
- Option B: The incoming alternator is the generator that is being synchronized with the other generator. The moving coil is not connected to the incoming alternator.
- Option D: Any of the above is not a correct answer.