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Materials and Components problems

2. A piece of copper and another piece of Germanium are cooled from 30�C to 80 K. The resistance of
Options
A. copper decreases and germanium increases
B. both decreases
C. both increases
D. copper increases and germanium decreases

5. Some ceramic materials become superconducting
Options
A. below liquid helium temperature
B. between liquid helium and liquid nitrogen temperature
C. above liquid nitrogen but below room temperature
D. at room temperature

6. As the temperature of semiconductor is increased
Options
A. the average number of free charge carriers decreases
B. the average number of free charge carriers increases
C. the average number of free charge carriers remains the same
D. the average number of free charge carriers may increase or decrease

7. For an insulating material, dielectric strength and dielectric losses should be
Options
A. high and high
B. low and high
C. high and low
D. low and low

9. Assertion (A): Ferrites are very useful at very high frequencies.
Reason (R): Ferrites have high permeability and high resistivity.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

10. If v is velocity of electron, ?₀ is absolute permittivity, m is mass of electron, e is charge on electron and r is the radius of orbit of electron in hydrogen atom, the stability of orbit requires the following equation to be satisfied
Options
A.
B.
C.
D.

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