(A) Cobalt, Nickel, Aluminium, Iron
(B) Permalloy, Nickel, Air, Water
(C) Silver, Copper, Aluminium, Iron
(D) Pure iron, Silicon iron. Aluminium, Bismuth.
2. In electrical machines the material preferred for pole shoes of electro-magnets is
(A) Pure iron
3. The percentage of silicon in transformer stampings is usually limited to
4. Find the odd one out
(C) Refractive index
(D) Dielectric strength.
5. Diamagnetic : Paramagnetic::
(A) Water: Air
(B) Iron: Steel
(C) Permalloy: Super-alloy
(D) Nickel: Cobalt.
6. If the permeability of a material is 0.999991. it can be classified as
(A) Diamagnetic material
(B) Paramagnetic material
(C) Ferro-magnetic material
7. Which of the following material has the highest permeability ?
(C) Pure iron
8. For a simplex lap winding, the commutator pitch is equal to
(B) ± 1
(D) ± 2.
9. If the resistivity of aluminium is 0.0283 x 10-6 Ω-m, the resistivity of copper could be
(A) 0.017 x 10-5 Ω-m
(B) 0.0382 x 10-5 Ω-m
(C) 0.0832 x 10-6 Ω-m
(D) 0.0889 x 10-6 Ω-m
10. Which variety of copper is used for overhead conductors ?
(A) Hard drawn copper
(B) Native copper
(C) Annealed copper
(D) Purest form of copper.
11. Annealed copper is used in
(A) low voltage cables
(B) flexible wires
(C) machine windings
(D) all of the above.
12. A ACSR conductor has central core of steel surrounded by a bunch of aluminium wires. In such conductors
(A) Current flows through aluminium conductors only
(B) Current flows through steel wire only
(C) Current flows through both steel as well as aluminium conductors
(D) Majority of current flows through aluminium and negligible amount flows through steel.
13. Which property of copper enables it to be drawn into thin wires and sheets ?
14. Which is non-magnetic material
15. Which of the following is the least desired property in magnetic materials for electrical engineering applications ?
(A) High magnetic permeability
(B) High electrical resistivity
(C) Large hysteresis loop
(D) All of the above.