Assertion (A): The resistance of a copper specimen changes by about 22% when tem

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Question
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

Correct Answer

Both A and R are true but R is not correct explanation of A

Explanation

The increase of resistance with temperature is governed by temperature coefficient of resistance.

Materials and Components problems

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1. 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

2. 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

4. Assertion (A): In Figure, the intercept of the line on y-axis is equal to N (a_e + a_i), where N is number of atoms/m³, a_e is electronic polarizability and a_i is ionic polarizability.
Reason (R): a_e and a_i are independent of temperature.
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

5. 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

6. 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

8. 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

10. 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

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