Conducting Materials – Exercise – 1

1. At low temperature, the resistivity of metals is proportional to the :

(a)  5th power of absolute temperature
(b)  6th power of absolute temperature
(c)  7th power of absolute temperature
(d)  9th power of absolute temperature

Answer
Answer : (a)
Explanation
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2. Which of the following doesn’t have forbidden energy gap between valence band and conductor band ?

(a)  conductor
(b)  insulator
(c)  semiconductor
(d)  none of the above

Answer
Answer : (a)
Explanation
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3. The electrical conductivity is directly proportional to :
(1) Electron density
(2) Relaxation time of electrons

(a)  both 1 & 2
(b)  only 2
(c)  only 1
(d)  neither 1 nor 2

Answer
Answer : (a)
Explanation
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4. The electron density in conduction band is proportional to :

(a)  donor concentration
(b)  square of donor concentration
(c)  square root of donor concentration
(d)  cube root of donor concentration

Answer
Answer : (c)
Explanation
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5. Which variety of copper has the best mechanical conductivity ?

(a)  Pure annealed copper
(b)  hard drawn copper
(c)  unpure annealed copper
(d)  cast copper

Answer
Answer : (a)
Explanation
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6. Which material has the highest electrical conductivity ?

(a)  Zinc
(b)  silver
(c)  brass
(d)  gold

Answer
Answer : (b)
Explanation
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7. Gold and silver are :

(a)  dielectric materials
(b)  low resistivity conducting materials
(c)  magnetic materials
(d)  insulating materials

Answer
Answer : (b)
Explanation
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8. The property due to which the resistance of some metal or compound vanishes under certain conditions is :

(a)  Semi conductivity
(b)  Super conductivity
(c)  Curie point
(d)  Magnetostriction

Answer
Answer : (b)
Explanation
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9. The conductivity of copper is less than that of silver by :

(a)  5 – 10 %
(b)  50 – 60 %
(c)  80 – 90 %
(d)  20 – 30 %

Answer
Answer : (a)
Explanation
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10. The conductivity of an extrinsic semiconductor :

(a)  decreases with temperature
(b)  increases with temperature
(c)  remains constant with temperature
(d)  decreases and then increases with temperature

Answer
Answer : (b)
Explanation
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