12. Magneticbearings are used in applications where noise and vibration are importantconsiderations or where lubricants are not acceptable. Like the hydrostatic bearings they do not require shaft rotation to generated bearing support forces. The rotor is floated in the space and levitated by magnetic forces, which are generated within the bearing by magnets. Therefore,
(A) the air is necessary to be used as the lubricant to provide the film pressure for magnetic bearings.
(B) the air is necessary to be used as the lubricant to reduce the noise and vibration for magnetic bearings.
(C) the shaft rotation is important for generating the supporting forces for the magnetic bearings.
(D) the magnetic forces are generated in the magnetic bearing to support the load of bearing.