# Design of Electrical Machines Questions and Answers – Bearings

This set of Design of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Bearings”.

1. What bearing is made use of in the horizontal shaft machines?
a) plain bearing
b) thrust bearing
c) push bearing
d) throw bearing

Explanation: The plain bearing is made use of in the horizontal shaft machine. The thrust bearing are used for vertical shaft machine.

2. What is the plain bearing used?
a) sleeve bearings
b) anti friction bearing
c) sleeve or anti friction bearing
d) sleeve and anti friction bearing

Explanation: The plain bearing can be the sleeve bearings made use of. It can also be friction bearings used which is either ball or roller bearings.

3. In horizontal shaft machines, the forces acting in which direction is prominent?
a) circular
b) vertical
c) horizontal

Explanation: Plain bearings are made use of for the horizontal shaft machines. The forces acting in the radial direction are most prominent.

4. In vertical shaft machines, which load is taken up by the thrust bearings?

Explanation: The thrust bearings are made use of for the vertical shaft machines. In vertical shaft machines, the axial load acting downwards is taken up by the thrust bearings.

a) dynamic unbalance of rotor
b) unbalanced magnetic pull of rotor
c) dynamic unbalance of rotor or unbalanced magnetic pull of rotor
d) dynamic unbalance of rotor and unbalanced magnetic pull of rotor

Explanation: The radial loads are caused by the dynamic unbalance of rotor. It can also be caused by the unbalanced magnetic pull of rotor.
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6. What is the additional setup provided to the simple thrust bearing when it is not able to take up radial loads?
a) ball bearing
b) gear bearing
c) steel bearing
d) guide bearing

Explanation: Sometimes the simple thrust bearing wont be able to pull the radial loads. Therefore an additional bearing called guide bearing is provided.

7. How many guide bearings are used along with the simple thrust bearings to pick up radial loads?
a) 2
b) 3
c) 2 or 3
d) 4

Explanation: The simple thrust bearing cannot pull the radial load and hence guide bearings are used in addition to it. Usually 2-3 guide bearings are used in vertical shaft machines depending upon the load.

8. Where are the bearings for the horizontal shaft placed?
a) outside the machine
b) in the end shields of the machine
c) outside the machine or in the end shields of the machine
d) outside the machine and in the end shields of the machine

Explanation: The bearings for the horizontal shaft machines are being placed outside the machine. It can also be placed along the end shields of the machine.

9. What is the other name of the bearings outside the machine?
a) ball bearing
b) pedestal bearing
c) guide bearing
d) gear bearing

Explanation: The bearings for the horizontal shaft machines are placed outside the machine or in the end shields of the machine. The other name for the bearings outside the machine is pedestal bearing.

10. The phosphor bronze sleeve bearings are used for the small electrical machines.
a) true
b) false

Explanation: The phosphor bronze sleeve bearings are used for the small electrical machines. The diameter of the machines are between 50-60 mm.

11. Anti-friction bearings are lubricated by charcoal.
a) true
b) false

Explanation: Anti-friction bearings are one type of bearing used to take radial loads. They are always lubricated by grease.

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