30.Magnetic bearings are used in applications where noise and vibration are importantconsiderations or where lubricants are not acceptable. Like the hydrostatic bearings theydo not require shaft rotation to generate bearing support forces. The rotor is floated in thespace and levitated by magnetic forces, which are generated within the bearing bymagnets. Therefore,
(A)the air is necessary to be used as the lubricant to provide the film pressure for magneticbearings.
(B)the air is necessary to be used as the lubricant to reduce the noise and vibration formagnetic bearings.
(C)the shaft rotation is important for generating the supporting forces for the magneticbearings.
(D)the magnetic forces are generated in the magnetic bearing to support the load ofbearing.