Permanent magnets are normally made of_____________?

Related Mcqs:

1. Hard steel is suitable for making permanent magnets because_____________?

   A. it has good residual magnetism B. its hysteresis loop has large area C. its mechanical strength is high D. its mechanical strength is low...

2. Those materials are well suited for making permanent magnets which have ________ retentivity and _________ coercivity

   A. low, high B. high, high C. high, low D. low, low...

3. When both the inductance and resistance of a coil are doubled the value of________________?

   A. time constant remains unchanged B. initial rate of rise of current is doubled C. final steady current is doubled D. time constant is halved...

4. Conductivity is analogous to____________?

   A. retentivity B. resistivity C. permeability D. inductance...

5. Laminated cores, in electrical machines, are used to reduce____________?

   A. copper loss B. eddy current loss C. hysteresis loss D. all of the above...

6. The unit of reluctance is_____________?

   A. metre/henry B. henry/metre C. henry D. 1/henry...

7. In a magnetic material hysteresis loss takes place primarily due to___________?

   A. rapid reversals of its magnetisation B. flux density lagging behind magnetising force C. molecular friction D. it high retentivity...

8. An air gap is usually inserted in magnetic circuits to____________?

   A. increase m.m.f. B. increase the flux C. prevent saturation D. none of the above...

9. The rate of rise of current through an inductive coil is maximum_____________?

   A. at 63.2% of its maximum steady value B. at the start of the current flow C. after one time constant D. near the final maximum value of current...

10. The initial rate of rise of current through a coil of inductance 10 H when suddenly connected to a D.C. supply of 200 V is__________Vs

    A. 50 B. 20 C. 0.05 D. 500...