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Materials And Components Online Exam Quiz

Important questions about Materials And Components. Materials And Components MCQ questions with answers. Materials And Components exam questions and answers for students and interviews.

1. 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 ? T 2 e -Ew/ k T .

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

2. Assertion (A): Silicon is the most favoured semiconductor material. Reason (R): PIV for silicon diode is more than that for germanium diode.

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

3. Assertion (A): Magnetism can be explained by the theory of magnetic domains. Reason (R): The existence of magnetic domains is evident from the Bitter powder patterns.

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

4. In crystalline solids, atoms are stacked in a regular manner.

Options

A : True

B : False

C :

D :

5. Orbital magnetic dipole moment is due to the motion of electron in its orbit around nucleus.

Options

A : True

B : False

C :

D :

6. In a piezoelectric crystal, the application of mechanical force will cause

Options

A : plastic deformation of crystal

B : magnetic dipoles in the crystal

C : electrical polarization in the crystal

D : shift in Fermi level

7. A piece of iron is placed in a magnetic field

Options

A : the magnetic field will not be affected

B : the magnetic lines of force will bend to pass through the piece

C : the magnetic lines of force will bend away from the piece

D : any of the above depending on type of iron

8. Assertion (A): If difference between static and optical dielectric constant is high, the mechanical compressiblity of that material is also high. Reason (R): For soft ions, ionic polarization per unit field is higher than that of hard ions.

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. Semi conducting materials are all

Options

A : elements

B : compounds

C : elements or compounds

D : elements or mixtures

1. In a metal, the drift velocity of electrons in the presence of a electric field E is

Options

A : proportional to E

B : proportional to E

C : inversely proportional to E

D : proportional to E 2

2. Inductors used at V.H.F. are made using

Options

A : air core

B : cast iron cored

C : sheet steel cored

D : thin film technique

3. Assertion (A): The resistance of a copper specimen changes by about 22% when temperature is increased from room temperature to 700°C. Reason (R): The physical properties of a material are determined mostly by the extent of impurities.

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

4. Assertion (A): For elemental dielectrics, P = N a e E i where N is number of atoms/m 3 , P is polarization, a e is electronic polarization and E i is internal electric field. Reason (R): In elemental dielectrics there are no permanent dipoles or ions.

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

6. If a capacitor C having selectivity factor Q is scaled down in all its dimensions by a factor K without any altering the dielectric material, the new capacitor will have capacitance and selectivity as

Options

A : C,

B : , Q

C : ,

D : C, K

7. Which solid dielectric has highest temperature limit?

Options

A : E

B : H

C : C

D : F

8. Assertion (A): An electron having charge - e and mass m and lying in an electric field E is subjected to an acceleration - ( e / m ) E. Reason (R): If there are n electrons/m 3 moving with velocity v x and each electron has a charge - e , the current density J = - n ev x .

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

9. Assertion (A): Orbital magnetic moment of an electron in an atom is of the order of 1 Bohr magneton. Reason (R): 1 Bohr magneton = 9.27 x 10 -24 A/m 2 .

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. When a pentavalent impurity is added, the semiconductor becomes

Options

A : p type

B : n type

C : intrinsic

D : neutral

2. Assertion (A): For most metals, Fermi energy E F is less than 10 eV. Reason (R): Fermi level of a metal is given by E F = 3.64 x 10 -19 ( n ) 2/3 where n is number of free electrons/m 3 of metal.

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

3. The relaxation time of electrons in a metal is of the order of

Options

A : 10 -6 secs

B : 10 -10 secs

C : 10 -14 secs

D : 10 -20 secs

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