# Materials and Components – Section 3

1. At a very low temperature, a semiconductor
 A. becomes a conductor B. becomes an insulator C. may become a conductor or an insulator D. will remain a semiconductor becomes a conductor or an insulator

Explanation:

Semi conductor becomes insulator at very low temperature.

2.  The colour code on a carbon resistor is red-red-black-silver. The value of resistor is
 A. 22000 Ω B. 2200 Ω C. 22 ± 5% Ω D. 22 ± 10% Ω

3.  Some typical examples of macroscopic quantities are
 A. conductivity B. µr C. dielectric constant D. all of the above

4.  The temperature coefficient of a thermistor
 A. is positive B. is negative C. zero D. may be positive or negative depending on its composition

5.  Assertion (A): Helium, Argon and Neon are gaseous at room temperature.

Reason (R): The atoms in Helium, Argon and Neon are chemically extremely inactive.

 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

6.  Resistivity of rubber is about
 A. 102 Ω-m B. 10-2 Ω-m C. 5 x 108 Ω m D. 5 x 1012 Ω-m

7.  An iron specimen has µr = 1000 when B = 0.3 T. If B = 0.35 T, µr
 A. will be 1000 B. will be less than 1000 C. will be more than 1000 D. may be more or less than 1000

8.  Which solid dielectric has highest temperature limit?
 A. E B. H C. C D. F

9.  Permeability is analogous to
 A. resistivity B. retentivity C. conductivity D. coercivity