Electrical Engineering Materials MCQ PDF Download

1. Aluminium does not corrode in atmosphere because

(a) it is a noble metal.
(b) atmospheric oxygen can only diffuse very slowly through the oxide layer which is formed on the surface of the aluminium.
(c) it does not react with oxygen.
(d) all of the above.

2. Carbon is………..material.

(a) conducting
(b) dielectric
(c) semiconducting
(d) non-conducting

3. In graphite, bonding is

(a) metallic.
(b) covalent.
(c) Vander Waals.
(d) van der Waals and covalent.

4. Graphite is a good lubricant because

(a) the sheets are bonded to one another by Vander Waals forces.
(b) the sheets are bonded to one another covaiently.
(c) both (a) and (b).
(d) none of these.

5. Constantan is an alloy composed of

(a) 86% copper, 12% manganese and 2% nickel.
(b) 76% nickel, 21% chromium, 2% manganese and 1% iron.
(c) 60% copper and 40% nickel.
(d) 40% copper, 40% nickel and 20% carbon.

6. Platinum is employed in

(a) electrical contacts and thermocouples.
(b) heating elements for electric furnaces.
(c) grids for special purpose vacuum tubes.
(d) all of the above.

7. ……..is employed as heating element for temperatures up to 1350°C.

(a) Nichrome
(b) Silicon carbide
(c) Copper
(d) Carbon

8. ………..is employed for winding of coils for dc motor starters.

(a) Constantan
(b) Nichrome
(c) Copper
(d) Aluminium

9. ………..has the highest operating temperature.

(a) Manganin
(b) Eureka
(c) Kanthal
(d) Nichrome

10. ………….has the lowest temperature coefficient of resistance.

(a) Nichrome
(b) Constantan
(c) Molybdenum
(d) Kanthal

11. Which of the following has zero temperature coefficient of resistance ?

(a) Manganin.
(b) Nichrome.
(c) Carbon.
(d) Aluminium.

12. A good electrical contact material should have the properties of

(a) high melting point.
(b) good thermal conductivity.
(c) high resistance to corrosion.
(d) high conductivity.
(e) all of the above.

13. Addition of 0.3 to 4.5% silicon to iron the electrical resistivity of iron

(a) increases.
(b) reduces.
(c) has no effect on.
(d) none of these.

14. Magnetic field of Earth has no vertical component at

(a) magnetic poles.
(b) magnetic equator.
(c) latitude 45⁰.
(d) longitude 45°. [I.E.S. E E.-I. 2011]

15. All magnetic materials lose their magnetic properties when

(a) cooled to low temperature.
(b) heated to high temperature.
(c) kept in an aluminium box.
(d) kept in vacuum. [I.E.S. E.E.-1, 2005]

16. Bohr magneton is unit of

(a) magnetic energy.
(b) permanent dipole moment due to spin.
(c) polarisability.
(d) hysteresis loss.

17. The magnetic field required to reduce the residual magnetisation to zero is called

(a) retentivity.
(b) coercivity.
(c) hysteresis.
(d) saturation magnetisation.

18. Consider the following statements:

The coercive force can be increased by

1. adding Cobalt because it is a ferromagnetic material.
2. adding Gold because it is a diamagnetic material.
3. adding Super alloy.
4. space charge polarizing.

Which of the above statements is/are correct?
(a) 1, 2, 3 and 4.
(b) 1 only.
(c) 2 only.
(d) 1 and 3 only. [I.E.S. E.E.-I, 2010]

19. Consider the following statements: Permanent magnet dipoles in matter result from

1. orbital angular momentum of electrons.
2. electron spin angular momentum.
3. nuclear spin angular momentum.

Which of these statements are correct?
(a) 1 and 2.
(b) 1 and 3.
(c) 2 and 3.
(d) 1, 2 and 3. [U.P.S.C. I.E.S. 1999]

20. Heating a permanent magnet results in the loss of magnetic behaviour because

(a) the atoms start vibrating.
(b) the magnetic dipoles start vibrating.
(c) the magnetic dipoles start realigning.
(d) the atoms start conducting.