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Materials and Components – Section 2(Page2)

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Materials and Components – Section 2

11. Semi conducting materials are all
A. elements
B. compounds
C. elements or compounds
D. elements or mixtures

Answer: Option C

Explanation:

Many compounds also show semiconducting properties.
12.  Silicon and germanium atoms combine orderly into array of atoms located in repetitive geometric pattern. This pattern is called
A. crystal
B. covalent bond
C. molecule
D. valence bond

Answer: Option A
13.  In a pure sample of silicon
A. the number of holes and free electrons is always equal
B. the number of free electrons is more than the number of holes
C. the number of free electrons and holes is equal at low temperature
D. the number of free electrons is less than number of holes

Answer: Option A
14.  Orbital magnetic dipole moment is due to the motion of electron in its orbit around nucleus.
A. True
B. False

Answer: Option A
15.  Assertion (A): ∈r can be determined experimentally by measuring the capacitance of a parallel plate capacitor with and without the dielectric.

Reason (R): Capacitance of a parallel plate capacitor =

.
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

Answer: Option A
16.  In a homogeneous magnetic field H of a solenoid, the core carries a magnetic dipole moment M per unit volume equal to
A. μ0 H
B. μr H
C. (μr – 1) H
D. μoμr H

Answer: Option C
17.  The field pattern of a solenoid is similar to that of bar magnet.
A. True
B. False

Answer: Option A
18.  Assertion (A): In a parallel plate capacitor having area of plate 1 m2 and plate separation 1 m, the capacitance C and resistance R are given by C = ∈0∈‘r and R = where ω is frequency, ∈r‘ and ∈r“ are real and imaginary parts of dielectric constant.

Reason (R): The imaginary part of electric constant is responsible for dielectric losses.
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

Answer: Option A
19.  Assertion (A): Silicon is the most favoured semiconductor material.

Reason (R): PIV for silicon diode is more than that for germanium diode.
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

Answer: Option C

Explanation:

Higher PIV for silicon is a definite advantage.
20.  Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.

Reason (R): Thermionic emission current ∝ T2 e-Ew/kT.
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

Answer: Option A

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