(A) a ferromagnetic material becomes paramagnetic
(B) a ferrite becomes an insulator
(C) a insulating material becomes a ferrite
(D) a diamagnetic material, becomes a paramagnetic material.
17. For a simplex wave winding, the winding pitch is equal to
(A) + 2
(B) – 2
(C) ± 1
(D) ± 2.
18. If yb is the back pitch and u is
the no. of coil sides per slot, then split coils can be avoided if the
following quantity is an integer
(A) (yb + 1)/ μ
(B) (yb + 1 )
(C) (yb – 1)/ μ
(D) (yb – 1)
19. Which of the following is a paramagnetic material ?
(C) Pure iron
(D) All of the above.
20. Which of the following is a ferromagnetic material ?
(A) Pure iron
21. For simplex wave and lap windings, the back pitch yb and front pitch yf are as follows:
(A) yb is odd, yf is even
(B) yb is even, yfis odd
(C) both yb and yf are odd
(D) both yb and yf are even.
22. All of the following are ferromagnetic materials EXCEPT
(D) Mild steel.
23. Diamagnetic: Copper:: Ferromagnetic:
24. Diamagnetic : Ferromagnetic ::
(A) Copper: Silver
(B) Air: Water
(C) Iron: Steel
(D) Lead: Cobalt.
25. Which of the following gives materials in order of increasing values of permeability ?
(A) Water, Iron. Copper, Silver
(B) Water, Air, Pure iron. Permalloy
(C) Cobalt, Aluminium, Copper, Silver
(D) Silicon iron. Palladium, Lead, Silver.
26. By adding silicon to ferromagnetic , materials
(A) electrical resistivity increases and also magnetic permeability increases
(B) electrical resistivity decreases and also magnetic permeability increases
(C) electrical resistivity decreases and magnetic permeability increases
(D) electrical resistivity increases and magnetic permeability decreases.
27. Which of the following can be worked with higher flux densities ?
(A) Mild steel
(B) Silicon iron
(C) Cold rolled silicon steel
(D) Hot rolled silicon steel.
28. Hysteresis loss varies with frequency (f) as
(B) f 1.6
(C) f 2
(D) f 2.6
29. Hysteresis loss varies with maximum flux density (B) as
30. In large bulky materials, the uni-axial anisotropy can be induced by
(A) cold rolling
(B) magnetic annealing
(C) magnetic quenching
(D) any of the above.