Materials and Components – Section 5(Page 2)

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Materials and Components – Section 5

11.The direction of force an a conductor carrying current and lying in a magnetic field can be found by using
A.Fleming’s left hand rule
B.Fleming’s right hand rule
C.Cork screw rule
D.Any of the above

Answer: Option A

12. Assertion (A): Rochelle salt and Barium titanate are both ferroelectric.

Reason (R): Ferroelectric materials exhibit hysteresis effect.

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 B

Explanation:

Both the materials exhibit ferroelectric properties. Hysteresis effect is one of the features of ferroelectric materials.

13. The units for electric dipole moment are
A.coulombs
B.colomb-metre
C.coulomb/metre
D.coulomb/m2

Answer: Option B

Explanation:

It is product of charge and distance.

14. The temperature coefficient of resistivity of semiconductors is
A.positive
B.negative
C.may be positive or negative
D.very low

Answer: Option B

Explanation:

Resistance of semiconductors decreases with increase in temperature.

15. Which of the following is used in automatic control of street lights?
A.Thermistor
B.Photoconductor
C.Transistor
D.Varistor

Answer: Option B

16. A leaky dielectric has ∈r = ∈r‘ – j∈r“. If a field E is applied, the current component in phase with E is proportional to ∈r“.
A.True
B.False

Answer: Option A

17. Assertion (A): In ionic dielectrics, P = Pe + Pi.

Reason (R): In ionic crystals, permanent electric dipole moment is zero.

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

Explanation:

In ionic dielectrics μp = ∑i ei ri and Po = 0.

Therefore P = Pe + Pi.

18. The current flow in a semiconductor is due to
A.holes
B.electrons
C.holes and electrons
D.holes, electrons and ions

Answer: Option C

19.Assertion (A): Relative permittivity is determined by the atomic structure of the material.

Reason (R): Absolute permittivity is determined by the atomic structure of the material.

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

20. Eddy current loss is
A.proportional to frequency
B.independent of frequency
C.proportional to (frequency)2
D.proportional to (frequency)3

Answer: Option C

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