Electrical Machine Design Objective Type Theory Practice - Set 09 - ObjectiveBooks

Electrical Machine Design Objective Type Theory Practice - Set 09

Practice Test: Question Set - 09

1. The length of air gap to be provided in __________ is primarily determined by power factor consideration.
    (A) D.C. series motor
    (B) D.C. shunt motor
    (C) Induction motor
    (D) Synchronous motor

2. The design of electromagnets is based upon which of the following fundamental equations?
    (A) Force equation
    (B) Magnetic circuit equation
    (C) Heating equation
    (D) All of the above

3. The laminations of the armature of a D.C. machine are usually ________ thick.
    (A) 0.1 to 0.2 mm
    (B) 0.2 to 0.3 mm
    (C) 0.3 to 0.4 mm
    (D) 0.4 to 0.5 mm

4. In a D.C. machine the number of brush arms is _____ the number of poles.
    (A) Less than
    (B) Equal to
    (C) Greater than
    (D) None of the above

5. Which of the following materials is used in the manufacture of resistance grids to be used in the starters of large motors?
    (A) Copper
    (B) Aluminium
    (C) Steel
    (D) Cast-iron

6. In ________ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft.
    (A) Small
    (B) Medium
    (C) Large
    (D) Any of the above

7. The change in flux linkages can be caused in which of the following ways?
    (A) The flux is constant with respect to time and is stationary and the coil moves through it
    (B) The coil is stationary with respect to flux and the flux varies in magnitude with respect to time
    (C) Both the changes mentioned above occur together, i.e., the coil moves through a time varying field
    (D) All of the above

8. Hot rolled sheets have _________ value of permeability
    (A) Zero
    (B) Low
    (C) High
    (D) None of the above

9. On which of the following variables heat convection depends?
    (A) Power density
    (B) Temperature difference between heated surface and coolant
    (C) Thermal resistivity, density, specific heat, Gravitational constant
    (D) All of the above

10. The resistivity of water should not be less than
    (A) 10 Q m
    (B) 100 Q m
    (C) 1000 Q m
    (D) 2000 Q m

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