The resistivity of water should not be less than_____________?

Related Mcqs:

1. In a D.C. machine the current per brush arm should not be more than_____________?

   A. 100 A
   B. 200 A
   E. 300 A
   D. 400 A

2. Materials exhibiting zero value of resistivity are known as ____________ ?

   A. conductors
   B. semiconductors
   C. insulators
   D. superconductors

3. The noise produced by a ___________ cooled machine is less as the rotor moves in a medium of smaller density?

   A. air
   B. hydrogen
   C. either A. or B.
   D. none of the above

4. Direct water cooling of rotor winding presents_____________?

   A. no mechanical difficulties
   B. lesser mechanical difficulties
   C. greater mechanical difficulties
   D. none of the above

5. With direct water cooling it is possible to have ratings of about_____________?

   A. 200 MW
   B. 300 MW
   C. 400 MW
   D. 600 MW

6. A current density of __________ is ilsed for large power transformers with forced circulation of oil or with water cooling coils?

   A. 1.5 to 2.5 A/mm2
   B. 3.5 to 4.5 A/mm2
   C. 4.0 to 5.0 A/mm2
   D. 5.4 to 6.2 A/mm2

7. __________ has a low relative permeability and is used principally in field frames when cost is of primary importance and extra weight is not objectionable?

   A. Cast steel
   B. Aluminium
   C. Soft steel
   D. Cast iron

8. cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall______________?

   A. Direct
   B. Indirect
   C. Conventional
   D. Any of the above

9. Which of the following is the commonly used type of electromagnets ?

   A. Flat-faced armature type
   B. Horse shoe type
   C. Flat-faced plunger type
   D. All of the above

10. D.C. servomotors are used in______________?

    A. purely D.C. control systems
    B. purely AC. control systems
    C. both D.C. and AC. control systems
    D. none of the above