Electrical Engineering Materials Multiple Choice Questions and Answers-4 (English)

1. A good electric contact material should have all of the following properties except
(A) high resistivity
(B) high resistance to corrosion
(C) good thermal conductivity
(D) high melting point
Ans: (A) high resistivity

2. Most of the common metals have _____ structure.
(A) linear
(B) hexagonal
(C) orthorhombic
(D) cubic
Ans: (D) cubic

3. Non-linear resistors
(A) produce harmonic distortion
(B) follows Ohm’s law at low temperatures only
(C) result in non-uniform heating
(D) none of the above
Ans: (A) produce harmonic distortion

4. A carbon resistor contains
(A) carbon crystals
(B) solid carbon granules
(C) pulverized coal
(D) finely divided carbon black.
Ans: (D) finely divided carbon black.

5. The impurity atoms is semiconductors
(A) inject more charge carriers
(B) reduce the energy gap
(C) increase the kinetic energy of valence electrons
(D) all of the above
Ans: (B) reduce the energy gap

6. Low resistivity materials are used in
(A) transformer, motor and generator windings
(B) transmission and distribution lines
(C) house wiring
(D) all above applications
Ans: (D) all above applications

7. The forbidden gap in an insulator is
(A) large
(B) small
(C) nil
(D) any of the above
Ans: (A) large

8. Which of the following factors affect resistivity of metals ?
(A) Age hardening
(B) Alloying
(C) Temperature
(D) All of the above
Ans: (D) All of the above

9. The conductivity of an extrinsic semiconductor with temperature
(A) decreases
(B) increases
(C) remains constant

(D) None of the above
Ans: (C) remains constant

10. The current due to electron flow in conduction band is the hole current in valence band.
(A) equal to
(B) less than
(C) greater than
(D) any of the above
Ans: (C) greater than

12. For a hole which of the following statements is incorrect ?
(A) Holes can exist in certain semiconductors only
(B) Holes can exist in any material including conductors
(C) Holes may constitute an electric current
(D) Holes can be considered as a net positive charge
Ans: (B) Holes can exist in any material including conductors

13. Surface resistance of an insulating material is reduced due to the
(A) smoky and dirty atmosphere
(B) humidity in the atmosphere
(C) both (A) and (b)
(D) neither (A) nor (b)
Ans: (C) both (A) and (b)

14. In conductors conduction of electricity takes place due to movement of
(A) electrons only
(B) positive ions only
(C) negative ions only
(D) positive and negative ions
Ans: (A) electrons only

15. The carbon percentage is least in
(A) low carbon steel
(B) wrought iron
(C) cast iron
(D) malleable iron
Ans: (B) wrought iron

16. Which of the following materials is the best conductor of electricity ?
(A) Tungsten
(B) Aluminium
(C) Copper
(D) Carbon
Ans: (C) Copper

17. Thermocouples are mainly used for the measurement of
(A) temperature
(B) resistance
(C) eddy currents
(D) coupling co-efficient
Ans: (A) temperature

18. _____ is a hard solder.
(A) Tin-lead
(6) Tin-silver-lead
(C) Copper-zinc
(D) None of the above
Ans: (C) Copper-zinc

19. Addition of 0.3 to 4.5% silicon to iron _____ the electrical resistivity of iron.
(A) increases
(B) decreases
(C) does not change

(D) None of the above
Ans: (A) increases

20. Super conductivity can be destroyed by
(A) adding impurities
(B) reducing temperatures
(C) application of magnetic field
(D) any of the above
Ans: (C) application of magnetic field