materials-and-components electronics-and-communication-engineering question and answers -Page 11

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Materials and Components problems

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 E²

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 = Na_eE_i where N is number of atoms/m³, 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

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/m³ 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/m².
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

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