electromagnets generally function as holding magnets ?

Related Mcqs:

1. The design of electromagnets is based upon which of the following fundamental equations ?

   A. Force equation
   B. Magnetic circuit equation
   C. Heating equation
   D. Voltage equation
   E. All of the above

2. 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

3. ____________are used for construction of core of electromagnets?

   A. Soft magnetic materials
   B. Hard magnetic materials
   C. Either A. or B.
   D. None of the above

4. Tractive magnets are operated from____________?

   A. a.c. supply
   B. d.c. supply
   C. either a.c. or d.c. supply
   D. none of the above

5. Commercial available medium size machines have a speed range of __________ ?

   A. 200 to 400 r.p.m
   B. 600 to 1000 r.p.m
   C. 1000 to 1500 r.p.m
   D. 2000 to 2500 r.p.m

6. The density of hydrogen is __________ times the density of air?

   A. 0.07
   B. 1.5
   C. 2.5
   D. 3.5

7. The weight of copper of both armature and field windings decreases with __________ in number of poles?

   A. increase
   B. decrease
   C. either of the above
   D. none of the above

8. Which of the following brushes can be used for high values of current density ?

   A. Metal graphite brushes
   B. Hard carbon brushes
   C. Electro-graphitic brushes
   D. Natural graphite brushes

9. The cold rolled grain oriented steel has ___________ permeability in the direction of the grain orientation?

   A. minimum
   B. maximum
   C. nil
   D. none of the above

10. The input impedance of a JFET is _____________that of an ordinary transistor?

    A. equal to
    B. less than
    C. more than
    D. none of the above