## PHYSICS- PAGE 4

1. If peak output voltage of a full wave rectifier is 10 V, its DC voltage is :

1) 10.0 V

2) 7.07 V

3) 6.36 V

4) 3.18 V

Ans: 3

2. A plane electromagnetic wave travelling in free space is incident normally on a glass plate of refractive index 3/2. If there is no absorption by the glass, its reflectivity is :

1) 4%

2) 16%

3) 20%

4) 50%

Ans: 1

3. Which one of the following cannot be explained by considering a harmonic approximation for the lattice vibrations in solids ?

1) Debye's T3 law

2) Dulong Petitt's Law

3) Optical branches in lattices

4) Thermal expansion

Ans: 4

4. High elastic modulus in materials arises from ,:

1) High strength of bonds

2) weak bonds

3) Combination of bonds

4) None

Ans: 1

5. In which of the following transitions will energy change be maximum ?

1) n = 5 to n = 4

2) n = 4 to n = 3

3) n = 3 to n = 2

4) n = 2 to n = 1

Ans: 4

6. Example for magnetic material used in data storage devices is :

1) 45 Permalloy

2) CrO2

3) Cunife

4) Alnico

Ans: 2

7. By saying that the electrostatic field is conservative , we do not mean that :

1) It is the gradient of a scalar potential

2) Its curl is identically zero

3) The work done in a closed path inside the field is zero

4) The potential difference between any two points is zero

Ans: 4

8. For a good conductor skin depth varies :

1) Directly as conductivity

2) inversely as conductivity

3) inversely as the square root of conductivity

4) Directly as the square root of conductivity

Ans: 3

9. Equipotentials at a great distance from a collection of charges whose total sum is not zero are approximately :

1) Spheres

2) Planes

3) Paraboloids

4) Ellipsoids

Ans: 1

10. The charge carrier density in the depletion layer of an unbiased pn junction is not ideally zero because of :

1) recombination

2) thermal pair production

3) drift

4) diffusion

Ans: 2

11. As one goes away from the center of an atom, the electron density :

1) decreases like Gaussian

2) decreases exponentially

3) oscillates with slowly decreasing amplitude

4) remains constant

Ans: 3

12. The fine structure of atomic spectral lines arises from :

1) electron spinorbit coupling

2) nuclear spin

3) interaction between electron and nucleus

4) interaction between atoms

Ans: 1

13. Two homonuclear diatomic molecules produce different rotational spectra, even though the atoms are known to have identical chemical properties. This leads to the conclusion that the atoms must be :

1) isotopes

2) isobars

3) isotones

4) isomers

Ans: 1

14. The total number of atoms in a unit cell of hcp structure is :

1) 4

2) 2

3) 6

4) 8

Ans: 3

15. Einstein's theory concludes that at lower temperature the specific heat of solids :

1) drops linearly with increase in temperature

2) drops linearly with decrease in temperature

3) drops exponentially with decrease in temperature

4) remains constant

Ans: 3

1) 10.0 V

2) 7.07 V

3) 6.36 V

4) 3.18 V

Ans: 3

2. A plane electromagnetic wave travelling in free space is incident normally on a glass plate of refractive index 3/2. If there is no absorption by the glass, its reflectivity is :

1) 4%

2) 16%

3) 20%

4) 50%

Ans: 1

3. Which one of the following cannot be explained by considering a harmonic approximation for the lattice vibrations in solids ?

1) Debye's T3 law

2) Dulong Petitt's Law

3) Optical branches in lattices

4) Thermal expansion

Ans: 4

4. High elastic modulus in materials arises from ,:

1) High strength of bonds

2) weak bonds

3) Combination of bonds

4) None

Ans: 1

5. In which of the following transitions will energy change be maximum ?

1) n = 5 to n = 4

2) n = 4 to n = 3

3) n = 3 to n = 2

4) n = 2 to n = 1

Ans: 4

6. Example for magnetic material used in data storage devices is :

1) 45 Permalloy

2) CrO2

3) Cunife

4) Alnico

Ans: 2

7. By saying that the electrostatic field is conservative , we do not mean that :

1) It is the gradient of a scalar potential

2) Its curl is identically zero

3) The work done in a closed path inside the field is zero

4) The potential difference between any two points is zero

Ans: 4

8. For a good conductor skin depth varies :

1) Directly as conductivity

2) inversely as conductivity

3) inversely as the square root of conductivity

4) Directly as the square root of conductivity

Ans: 3

9. Equipotentials at a great distance from a collection of charges whose total sum is not zero are approximately :

1) Spheres

2) Planes

3) Paraboloids

4) Ellipsoids

Ans: 1

10. The charge carrier density in the depletion layer of an unbiased pn junction is not ideally zero because of :

1) recombination

2) thermal pair production

3) drift

4) diffusion

Ans: 2

11. As one goes away from the center of an atom, the electron density :

1) decreases like Gaussian

2) decreases exponentially

3) oscillates with slowly decreasing amplitude

4) remains constant

Ans: 3

12. The fine structure of atomic spectral lines arises from :

1) electron spinorbit coupling

2) nuclear spin

3) interaction between electron and nucleus

4) interaction between atoms

Ans: 1

13. Two homonuclear diatomic molecules produce different rotational spectra, even though the atoms are known to have identical chemical properties. This leads to the conclusion that the atoms must be :

1) isotopes

2) isobars

3) isotones

4) isomers

Ans: 1

14. The total number of atoms in a unit cell of hcp structure is :

1) 4

2) 2

3) 6

4) 8

Ans: 3

15. Einstein's theory concludes that at lower temperature the specific heat of solids :

1) drops linearly with increase in temperature

2) drops linearly with decrease in temperature

3) drops exponentially with decrease in temperature

4) remains constant

Ans: 3

16. Which of the following is not true for pelitier's effect :

1) It is a reversible effect

2) It takes place only at the junctions

3) It is independent of the direction of current

4) It may be heating or cooling effect

Ans: 3

17. The number of independent elastic constants in an isotropic cubic solid is :

1) 1

2) 3

3) 9

4) 12

Ans: 2

18. The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called :

1) curie temperature

2) neel temprature

3) weiss temperature

4) faraday's temperature

Ans: 2

19. The susceptibility of a dimagnetic material is essentially independent of temperature :

1) under all circumstances

2) as long as the electronic structure is independent of temperature.

3) at very low temperatures of the order of 10 K

4) at very high temperature

Ans: 2

20. Vibrational states of a diatomic molecule are seperated by energy interval of the order of :

1) 0.001 eV

2) 0.1 eV

3) 10 eV

4) 100 eV

Ans: 2

21. Which of the following series is observed in absorption spectra of alkali atoms:

1) Principal only

2) Principal and sharp only

3) Principal , sharp and diffuse only

4) Principal , sharp, diffuse and fundamental

Ans: 1

22. For a face centered cubic crystalline structure the following diffraction peaks may be observed in the Xray diffraction experiment :

1) (110), (330)

2) (111), (321)

3) (100), (321)

4) (111), (331)

Ans: 4

23. Identify the statement that is not true for ferromagnetic materials :

1) They have a large magnetic susceptibility

2) They have a fixed value of relative permeability

3) Energy loss is proportional to the area of hysteresis loop

4) They lose their nonlinearity property above the curie temperature

Ans: 2

24. An electron makes a transition from the valance band to the conduction band in an indirect band gap semiconductor . Which of the following is NOT true ?

1) There is no momentum change in the electron .

2) A phonon is involved in the process

3) A photon is involved in the process

4) The energy of the electron increases

Ans: 1

25. A series RLC circuit is resonant at 1 MHz. At 1.1 MHz the circuit impedence is :

1) Capacitive

2) Inductive

3) Resistive

4) Minimum

Ans: 2

1) It is a reversible effect

2) It takes place only at the junctions

3) It is independent of the direction of current

4) It may be heating or cooling effect

Ans: 3

17. The number of independent elastic constants in an isotropic cubic solid is :

1) 1

2) 3

3) 9

4) 12

Ans: 2

18. The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called :

1) curie temperature

2) neel temprature

3) weiss temperature

4) faraday's temperature

Ans: 2

19. The susceptibility of a dimagnetic material is essentially independent of temperature :

1) under all circumstances

2) as long as the electronic structure is independent of temperature.

3) at very low temperatures of the order of 10 K

4) at very high temperature

Ans: 2

20. Vibrational states of a diatomic molecule are seperated by energy interval of the order of :

1) 0.001 eV

2) 0.1 eV

3) 10 eV

4) 100 eV

Ans: 2

21. Which of the following series is observed in absorption spectra of alkali atoms:

1) Principal only

2) Principal and sharp only

3) Principal , sharp and diffuse only

4) Principal , sharp, diffuse and fundamental

Ans: 1

22. For a face centered cubic crystalline structure the following diffraction peaks may be observed in the Xray diffraction experiment :

1) (110), (330)

2) (111), (321)

3) (100), (321)

4) (111), (331)

Ans: 4

23. Identify the statement that is not true for ferromagnetic materials :

1) They have a large magnetic susceptibility

2) They have a fixed value of relative permeability

3) Energy loss is proportional to the area of hysteresis loop

4) They lose their nonlinearity property above the curie temperature

Ans: 2

24. An electron makes a transition from the valance band to the conduction band in an indirect band gap semiconductor . Which of the following is NOT true ?

1) There is no momentum change in the electron .

2) A phonon is involved in the process

3) A photon is involved in the process

4) The energy of the electron increases

Ans: 1

25. A series RLC circuit is resonant at 1 MHz. At 1.1 MHz the circuit impedence is :

1) Capacitive

2) Inductive

3) Resistive

4) Minimum

Ans: 2

26. S.I unit of force is :

(A) kgf (B) newton (C) pascal (D) kg/cm2

Ans: B

27. The permissible variation of a size is called :

(A) Limit (B) Allowance (C) Tolerence (D) Fit

Ans: C

28. Quantum theory introduced by

(A) Einstein (B) Isaac Newton

(C) Michale Faradey (D) Max Plank

Ans: D

29. What is the unit of energy ?

(A) Newton (B) Kilometre

(C) Joule (D) Decibel

Ans: C

30. The energy gap between the valence band and conduction band for a material is above 6 eV. The material is __________.

(A) super conductor (B) an insulator (C) a dopped semiconductor (D) a conductor

Ans: B

31. Radius of first orbit of hydrogen atom is 0.53 Å. So the radius of the second orbit will be __________.

(A) 2.12 Å (B) 4.77 Å (C) 1.06 Å (D) 0.27Å

Ans: A

32. The work done in moving a charge ‘q’ on an equipotential surface is __________.

(A) infinity (B) 0 (C) q/2 (D) 2q

Ans: B

33. When light of suitable frequency falls on certain metal surfaces, electrons are emitted from it. This phenomenon is known as __________. (A) Meissner effect

(B) Zeeman effect

(C) Total internal reflection

(D) Photoelectric effect

Ans: D

34. The core of the transformer is laminated to __________.

(A) Increase the magnetic flux linked with it

(B) Increase the flux leakage

(C) Reduce the power loss due to eddy current

(D) Reduce the hysteresis loss

Ans: C

(A) kgf (B) newton (C) pascal (D) kg/cm2

Ans: B

27. The permissible variation of a size is called :

(A) Limit (B) Allowance (C) Tolerence (D) Fit

Ans: C

28. Quantum theory introduced by

(A) Einstein (B) Isaac Newton

(C) Michale Faradey (D) Max Plank

Ans: D

29. What is the unit of energy ?

(A) Newton (B) Kilometre

(C) Joule (D) Decibel

Ans: C

30. The energy gap between the valence band and conduction band for a material is above 6 eV. The material is __________.

(A) super conductor (B) an insulator (C) a dopped semiconductor (D) a conductor

Ans: B

31. Radius of first orbit of hydrogen atom is 0.53 Å. So the radius of the second orbit will be __________.

(A) 2.12 Å (B) 4.77 Å (C) 1.06 Å (D) 0.27Å

Ans: A

32. The work done in moving a charge ‘q’ on an equipotential surface is __________.

(A) infinity (B) 0 (C) q/2 (D) 2q

Ans: B

33. When light of suitable frequency falls on certain metal surfaces, electrons are emitted from it. This phenomenon is known as __________. (A) Meissner effect

(B) Zeeman effect

(C) Total internal reflection

(D) Photoelectric effect

Ans: D

34. The core of the transformer is laminated to __________.

(A) Increase the magnetic flux linked with it

(B) Increase the flux leakage

(C) Reduce the power loss due to eddy current

(D) Reduce the hysteresis loss

Ans: C

35. Choose the only false statement from the following :

1) Substances with energy gap of the order of 10 eV are insulators

2) The conductivity of a semiconductor increases with increases in temperature

3) In conductors the valence and conduction bands may overlap

4) The resistivity of a semiconductor increases with increase in temperature

Ans: 4

36. The moment of inertia of a uniform circular disc of radius R and mass M about an axis passing from the edge of the disc and normal to the disc is :

1) (5/2)MR2

2) MR2

3) (7/2)MR2

4) (3/2)MR2

Ans: 4

37. Copper has face-centered cubic (fcc) lattice with interatomic spacing equal to 2.54 Å. The value of lattice constant for this lattice is :

1) 2.29 Å

2) 3.29 Å

3) 2.59 Å

4) 3.59 Å

Ans: 4

38. The total energy of an electron in the first excited state of hydrogen is about - 3.4 eV. Its kinetic energy in this state is :

1) - 3.4 eV 2) - 1.7 eV 3) 1.7 eV 4) 3.4 eV

Ans: 4

39. For a satellite moving in an orbit around the earth, the ratio of kinetic energy to potential energy is :

1) 4 2) 1/2 3) 1/√2 4) 1/4

Ans: 2

40. A ball is thrown vertically upward. It has a speed of 10 m/s when it has reached one half of its maximum height. How high does the ball rise ? (Taking g = 10 m/s2)

1) 6 m 2) 10 m 3) 14 m 4) 18 m

Ans: 2

1) Substances with energy gap of the order of 10 eV are insulators

2) The conductivity of a semiconductor increases with increases in temperature

3) In conductors the valence and conduction bands may overlap

4) The resistivity of a semiconductor increases with increase in temperature

Ans: 4

36. The moment of inertia of a uniform circular disc of radius R and mass M about an axis passing from the edge of the disc and normal to the disc is :

1) (5/2)MR2

2) MR2

3) (7/2)MR2

4) (3/2)MR2

Ans: 4

37. Copper has face-centered cubic (fcc) lattice with interatomic spacing equal to 2.54 Å. The value of lattice constant for this lattice is :

1) 2.29 Å

2) 3.29 Å

3) 2.59 Å

4) 3.59 Å

Ans: 4

38. The total energy of an electron in the first excited state of hydrogen is about - 3.4 eV. Its kinetic energy in this state is :

1) - 3.4 eV 2) - 1.7 eV 3) 1.7 eV 4) 3.4 eV

Ans: 4

39. For a satellite moving in an orbit around the earth, the ratio of kinetic energy to potential energy is :

1) 4 2) 1/2 3) 1/√2 4) 1/4

Ans: 2

40. A ball is thrown vertically upward. It has a speed of 10 m/s when it has reached one half of its maximum height. How high does the ball rise ? (Taking g = 10 m/s2)

1) 6 m 2) 10 m 3) 14 m 4) 18 m

Ans: 2

41. In producing chlorine through electrolysis 100 W power at 125 V is being consumed. How much chlorine per min is liberated ? ECE of chlorine is 0.367 x 10-6 kg/C :

1) 17.6 mg

2) 34.3 mg

3) 24.3 mg

4) 39.6 mg

Ans: 1

42. A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency ?

1) 275 K

2) 175 K

3) 250 K

4) 225 K

Ans: 3

43. Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances r1 and r2 (r1 > r2) respectively. When the circuit is closed, the potential difference across the first cell is zero, The value of R is :

1) r1 - r2

2) (r1 + r2)/2

3) (r1 - r2)/2

4) r1 + r2

Ans: 1

44. A black body at 1227°C emits radiations with maximum intensity at a wavelength of 5000 Å. If the temperature of the body is increased by 1000°C, the maximum intensity will be observed at :

1) 7500 Å

2) 1500 Å

3) 6000 Å

4) 3000 Å

Ans: 4

45. Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potential difference applied across them so that the magnetic field at their centres is the same ?

1) 5

2) 4

3) 7

4) 2

Ans: 2

46. A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be :

1) f/4

2) 8f

3) f/2√2

4) 2f

Ans: 3

47. The binding energy of deuteron is 2.2 MeV and that of 42He is 28 MeV. If two deuterons are fused to form one 42He then the energy released is :

1) 21.6 MeV

2) 23.6 MeV

3) 17.2 MeV

4) 28.2 MeV

Ans: 2

48. In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. If the decay constant of the material is λ, then :

1) R1 = R2 e-λ(t1 -t2 )

2) R1 = R2 eλ(t1 -t2 )

3) R1 = R2 e(t2 /t1 )

4) R1 = R2

Ans: 1

49. Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emitted by hydrogen will be :

1) two

2) three

3) four

4) one

Ans: 2

50. The potential energy of a long spring when stretched by 2 cm is U. If the spring is stretched by 8 cm the potential energy stored in it is : 1) 4U

2) U/8

3) 16U

4) U/4

Ans: 3

51. For angles of projection of a projectile at angles (45°θ) and (45° +θ), the horizontal - ranges described by the projectile are in the ratio of :

1) 1 : 1

2) 2 : 3

3) 1 : 2

4) 3 : 2

Ans: 1

52. A body of mass 3 kg is under a constant force which causes a displacement s in metres in it, given by the relation s = (1/3) t2, where t is in s. Work done by the force in 2 s is :

1) (17/3)J

2) (3/8)J

3) (8/3)J

4) (3/17)J

Ans: 3

53. A particle moves along a straight line OX. At a time t (in seconds) the distance x (in metres) of the particle from O is given by x = 40 + 12t - t3 How long would the particle travel before coming to rest ?

1) 14 m

2) 28 m

3) 56 m

4) 70 m

Ans: 3

54. The velocity v of a particle at time t is given by v = at + (b/t + c), where a, b and c are constants, The dimensions of a, b and c are

constants, The dimensions of a, b and c are respectively :

1) [LT -2], [L] and [T]

2) [L], [T] and [LT 2]

3) [L2T 2], [LT] and [L]

4) [L], [LT] and [T 2]

Ans: 1

55. A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again ?

1) 1 cm upward

2) 0.5 cm downward

3) 1 cm downward

4) 0.5 cm upward

Ans: 1

56. 300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Taking g =10 m/s2, work done against friction is :

1) 50 J

2) 100 J

3) zero

4) 150 J

Ans: 2

57. A transistor is operated in common emitter configuration at constant collector voltage Vc = 1.5 V such that a change in the base current from 100 µA to 150 µA produces a change in the collector current from 5 mA to 10 mA. The current gain (β) is :

1) 50

2) 75

3) 100

4) 125

Ans: 3

58. A photo-cell employs photoelectric effect to convert :

1) change in the frequency of light into a change in electric voltage

2) change in the intensity of illumination into a change in photoelectric current

3) change in the intensity of illumination into a change in the work function of the photocathode

4) change in the frequency of light into a change in the electric current

Ans: 2

59. The core of a transformer is laminated because :

1) energy losses due to eddy currents may be minimized

2) the weight of the transformer may be reduced

3) rusting of the core may be prevented

4) ratio of voltage in primary and secondary may be increased

Ans: 1

60. Two coils of self-inductances 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is :

1) 8 mH

2) 12 mH

3) 4 mH

4) 16 mH

Ans: 3

61. In a discharge tube ionization of enclosed gas is produced due to collisions between :

1) positive ions and neutral atoms/molecules

2) negative electrons and neutral atoms/molecules

3) photons and neutral atoms/molecules

4) neutral gas atoms/molecules

Ans: 2

62. When photons of energy hv fall on an aluminium plate (of work function E0), photoelectrons of maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be :

1) K + E0

2) 2K

3) K

4) k + hv

Ans: 4

63. A coil of inductive reactance 31 has a resistance of Ω. It is placed in series with a Ω 8 condenser of capacitative reactance 25Ω. The combination is connected to an a.c. soruce of 110 V. The power factor of the circuit is :

1) 0.40

2) 0.128

3) 0.80

4) 0.66

Ans: 3

64. The moment of inertia of a uniform circular disc of radius R and mass M about an axis touching the disc at its diameter and normal to the disc is :

1) MR2

2) (2/5)MR2

3) (3/5)MR2

4) (5/6)MR2

Ans: 3

65. The momentum of a photon of energy 1 MeV in kg m/s, will be :

1) 0.33 x 106

2) 8 x 10-24

3) 5 x 10-23

4) 5 x 10-22

Ans: 4

66. The radius of germanium (Ge) nuclide is measured to be twice the radius of 94Be. The number of nucleons in Ge are :

1) 73

2) 74

3) 76

4) 72

Ans: 4

67. The molar specific heat at constant pressure of an ideal gas is (7/2)R. The ratio of specific heat at constant pressure to that at constant volume is :

1) 7/5

2) 6/7

3) 9/7

4) 4/7

Ans: 1

68. The earth is assumed to be a sphere of radius R. A platform is arranged at a height R from the surface of the earth. The escape velocity of a body from this platform is fve, where ve is its escape velocity from the surface of the earth. The value of f is :

1) 2

2) 1/√2

3) 1/3

4) 1

Ans: 2

69. Two sound waves with wavelengths 5.0 m and 5.5 m respectively, each propagate in a gas with velocity 330 m/s. We expect the following number of beats per second :

1) 12 2) 0 3) 3 4) 6

Ans: 4

70. Kirchhoff's first and second laws for electrical circuits are consequences of :

1) conservation of energy 2) conservation of electric charge and energy respectively

3) conservation of electric charge 4) conservation of energy and electric charge respectively

Ans: 2

71. A transverse wave propagating along x-axis is represented by : y(x, t) = 8.0 sin (0.5πx - 4πt - (π/4)) where x is in metres and t is in seconds. The speed of the wave is :

1) 8π m/s 2) 0.5π m/s 3) (π/4) m/s 4) 8 m/s

Ans: 4

72. The time of reverberation of a room A is one second. What will be the time (in seconds) of reverberation of a room, having all the dimensions double of those of room A ?

1) 2 2) 4 3) 1/2 4) 8

Ans: 1

73. Which one of the following statements is true ?

1) Both light and sound waves in air are transverse

2) The sound waves in air are longitudinal while the light waves are transverse

3) Both light and sound waves in air are longitudinal

4) Both light and sound waves can travel in vacuum

Ans: 2

74. Above Curie temperature :

1) a ferromagnetic substance becomes paramagnetic

2) a paramagnetic substance becomes diamagnetic

3) a diamagnetic substance becomes paramagnetic

4) a paramagnetic substance becomes ferromagnetic

Ans: 1

75. A convex lens and a concave lens, each having same focal length of 25 cm, are put in contact to form a combination of lenses. The power in diopters of the combination is :

1) 25 2) 50 3) infinite 4) zero

Ans: 4

76. A parallel plate air capacitor is charged to a potential difference of V volts. After disconnecting the charging battery the distance between the plates of the capacitor is increased using an insulating handle. As a result the potential difference between the plates :

1) decreases 2) does not change 3) becomes zero 4) increases

Ans: 4

77. A car runs at a constant speed on a circular track of radius 100 m, taking 62.8 s for every circular lap. The average velocity and average speed for each circular lap respectively is :

1) 0, 0 2) 0, 10 m/s 3) 10 m/s, 20 m/s 4) 20 m/s, 0

Ans: 2

78. A tube of length L is filled completely with an incompressible liquid of mass M and closed at both the ends. The tube is then rotated in a horizontal plane about one of its ends with a uniform angular velocity ω. The force exerted by the liquid at the other end is :

1) (MLω 2)/(2) 2) (ML2ω)/(2) 3) 2MLω 2 4) (ML2ω 2)/(2)

Ans: 1

79. Two bodies, A (of mass 1 kg) and B (of mass 3 kg) are dropped from heights of 16 m and 25 m, respectively. The ratio of the time taken by them to reach the ground is :

1) 5/4 2) 8/5 3) 5/8

Ans: 4

1) 17.6 mg

2) 34.3 mg

3) 24.3 mg

4) 39.6 mg

Ans: 1

42. A Carnot engine whose sink is at 300 K has an efficiency of 40%. By how much should the temperature of source be increased so as to increase its efficiency by 50% of original efficiency ?

1) 275 K

2) 175 K

3) 250 K

4) 225 K

Ans: 3

43. Two cells, having the same emf, are connected in series through an external resistance R. Cells have internal resistances r1 and r2 (r1 > r2) respectively. When the circuit is closed, the potential difference across the first cell is zero, The value of R is :

1) r1 - r2

2) (r1 + r2)/2

3) (r1 - r2)/2

4) r1 + r2

Ans: 1

44. A black body at 1227°C emits radiations with maximum intensity at a wavelength of 5000 Å. If the temperature of the body is increased by 1000°C, the maximum intensity will be observed at :

1) 7500 Å

2) 1500 Å

3) 6000 Å

4) 3000 Å

Ans: 4

45. Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potential difference applied across them so that the magnetic field at their centres is the same ?

1) 5

2) 4

3) 7

4) 2

Ans: 2

46. A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be :

1) f/4

2) 8f

3) f/2√2

4) 2f

Ans: 3

47. The binding energy of deuteron is 2.2 MeV and that of 42He is 28 MeV. If two deuterons are fused to form one 42He then the energy released is :

1) 21.6 MeV

2) 23.6 MeV

3) 17.2 MeV

4) 28.2 MeV

Ans: 2

48. In a radioactive material the activity at time t1 is R1 and at a later time t2, it is R2. If the decay constant of the material is λ, then :

1) R1 = R2 e-λ(t1 -t2 )

2) R1 = R2 eλ(t1 -t2 )

3) R1 = R2 e(t2 /t1 )

4) R1 = R2

Ans: 1

49. Ionization potential of hydrogen atom is 13.6 eV. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy 12.1 eV. According to Bohr's theory, the spectral lines emitted by hydrogen will be :

1) two

2) three

3) four

4) one

Ans: 2

50. The potential energy of a long spring when stretched by 2 cm is U. If the spring is stretched by 8 cm the potential energy stored in it is : 1) 4U

2) U/8

3) 16U

4) U/4

Ans: 3

51. For angles of projection of a projectile at angles (45°θ) and (45° +θ), the horizontal - ranges described by the projectile are in the ratio of :

1) 1 : 1

2) 2 : 3

3) 1 : 2

4) 3 : 2

Ans: 1

52. A body of mass 3 kg is under a constant force which causes a displacement s in metres in it, given by the relation s = (1/3) t2, where t is in s. Work done by the force in 2 s is :

1) (17/3)J

2) (3/8)J

3) (8/3)J

4) (3/17)J

Ans: 3

53. A particle moves along a straight line OX. At a time t (in seconds) the distance x (in metres) of the particle from O is given by x = 40 + 12t - t3 How long would the particle travel before coming to rest ?

1) 14 m

2) 28 m

3) 56 m

4) 70 m

Ans: 3

54. The velocity v of a particle at time t is given by v = at + (b/t + c), where a, b and c are constants, The dimensions of a, b and c are

constants, The dimensions of a, b and c are respectively :

1) [LT -2], [L] and [T]

2) [L], [T] and [LT 2]

3) [L2T 2], [LT] and [L]

4) [L], [LT] and [T 2]

Ans: 1

55. A microscope is focussed on a mark on a piece of paper and then a slab of glass of thickness 3 cm and refractive index 1.5 is placed over the mark. How should the microscope be moved to get the mark in focus again ?

1) 1 cm upward

2) 0.5 cm downward

3) 1 cm downward

4) 0.5 cm upward

Ans: 1

56. 300 J of work is done in sliding a 2 kg block up an inclined plane of height 10 m. Taking g =10 m/s2, work done against friction is :

1) 50 J

2) 100 J

3) zero

4) 150 J

Ans: 2

57. A transistor is operated in common emitter configuration at constant collector voltage Vc = 1.5 V such that a change in the base current from 100 µA to 150 µA produces a change in the collector current from 5 mA to 10 mA. The current gain (β) is :

1) 50

2) 75

3) 100

4) 125

Ans: 3

58. A photo-cell employs photoelectric effect to convert :

1) change in the frequency of light into a change in electric voltage

2) change in the intensity of illumination into a change in photoelectric current

3) change in the intensity of illumination into a change in the work function of the photocathode

4) change in the frequency of light into a change in the electric current

Ans: 2

59. The core of a transformer is laminated because :

1) energy losses due to eddy currents may be minimized

2) the weight of the transformer may be reduced

3) rusting of the core may be prevented

4) ratio of voltage in primary and secondary may be increased

Ans: 1

60. Two coils of self-inductances 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is :

1) 8 mH

2) 12 mH

3) 4 mH

4) 16 mH

Ans: 3

61. In a discharge tube ionization of enclosed gas is produced due to collisions between :

1) positive ions and neutral atoms/molecules

2) negative electrons and neutral atoms/molecules

3) photons and neutral atoms/molecules

4) neutral gas atoms/molecules

Ans: 2

62. When photons of energy hv fall on an aluminium plate (of work function E0), photoelectrons of maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be :

1) K + E0

2) 2K

3) K

4) k + hv

Ans: 4

63. A coil of inductive reactance 31 has a resistance of Ω. It is placed in series with a Ω 8 condenser of capacitative reactance 25Ω. The combination is connected to an a.c. soruce of 110 V. The power factor of the circuit is :

1) 0.40

2) 0.128

3) 0.80

4) 0.66

Ans: 3

64. The moment of inertia of a uniform circular disc of radius R and mass M about an axis touching the disc at its diameter and normal to the disc is :

1) MR2

2) (2/5)MR2

3) (3/5)MR2

4) (5/6)MR2

Ans: 3

65. The momentum of a photon of energy 1 MeV in kg m/s, will be :

1) 0.33 x 106

2) 8 x 10-24

3) 5 x 10-23

4) 5 x 10-22

Ans: 4

66. The radius of germanium (Ge) nuclide is measured to be twice the radius of 94Be. The number of nucleons in Ge are :

1) 73

2) 74

3) 76

4) 72

Ans: 4

67. The molar specific heat at constant pressure of an ideal gas is (7/2)R. The ratio of specific heat at constant pressure to that at constant volume is :

1) 7/5

2) 6/7

3) 9/7

4) 4/7

Ans: 1

68. The earth is assumed to be a sphere of radius R. A platform is arranged at a height R from the surface of the earth. The escape velocity of a body from this platform is fve, where ve is its escape velocity from the surface of the earth. The value of f is :

1) 2

2) 1/√2

3) 1/3

4) 1

Ans: 2

69. Two sound waves with wavelengths 5.0 m and 5.5 m respectively, each propagate in a gas with velocity 330 m/s. We expect the following number of beats per second :

1) 12 2) 0 3) 3 4) 6

Ans: 4

70. Kirchhoff's first and second laws for electrical circuits are consequences of :

1) conservation of energy 2) conservation of electric charge and energy respectively

3) conservation of electric charge 4) conservation of energy and electric charge respectively

Ans: 2

71. A transverse wave propagating along x-axis is represented by : y(x, t) = 8.0 sin (0.5πx - 4πt - (π/4)) where x is in metres and t is in seconds. The speed of the wave is :

1) 8π m/s 2) 0.5π m/s 3) (π/4) m/s 4) 8 m/s

Ans: 4

72. The time of reverberation of a room A is one second. What will be the time (in seconds) of reverberation of a room, having all the dimensions double of those of room A ?

1) 2 2) 4 3) 1/2 4) 8

Ans: 1

73. Which one of the following statements is true ?

1) Both light and sound waves in air are transverse

2) The sound waves in air are longitudinal while the light waves are transverse

3) Both light and sound waves in air are longitudinal

4) Both light and sound waves can travel in vacuum

Ans: 2

74. Above Curie temperature :

1) a ferromagnetic substance becomes paramagnetic

2) a paramagnetic substance becomes diamagnetic

3) a diamagnetic substance becomes paramagnetic

4) a paramagnetic substance becomes ferromagnetic

Ans: 1

75. A convex lens and a concave lens, each having same focal length of 25 cm, are put in contact to form a combination of lenses. The power in diopters of the combination is :

1) 25 2) 50 3) infinite 4) zero

Ans: 4

76. A parallel plate air capacitor is charged to a potential difference of V volts. After disconnecting the charging battery the distance between the plates of the capacitor is increased using an insulating handle. As a result the potential difference between the plates :

1) decreases 2) does not change 3) becomes zero 4) increases

Ans: 4

77. A car runs at a constant speed on a circular track of radius 100 m, taking 62.8 s for every circular lap. The average velocity and average speed for each circular lap respectively is :

1) 0, 0 2) 0, 10 m/s 3) 10 m/s, 20 m/s 4) 20 m/s, 0

Ans: 2

78. A tube of length L is filled completely with an incompressible liquid of mass M and closed at both the ends. The tube is then rotated in a horizontal plane about one of its ends with a uniform angular velocity ω. The force exerted by the liquid at the other end is :

1) (MLω 2)/(2) 2) (ML2ω)/(2) 3) 2MLω 2 4) (ML2ω 2)/(2)

Ans: 1

79. Two bodies, A (of mass 1 kg) and B (of mass 3 kg) are dropped from heights of 16 m and 25 m, respectively. The ratio of the time taken by them to reach the ground is :

1) 5/4 2) 8/5 3) 5/8

Ans: 4

80. The primary and secondary coil of a transformer have 50 and 1500 turns respectively. If the magnetic flux φ linked with the primary coil is given by φ = φ0 + 4t, where φ is in webers, t is time in seconds and φ0 is a constant, the output voltage across the secondary coil is

(a) 120 volts (b) 220 volts (c) 30 volts (d) 90 volts

Ans: A

81. A beam of electron passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move

(a) in a circular orbit (b) along a parabolic path

(c) along a straight line (d) in an elliptical orbit.

Ans: A

82. The position x of a particle with respect to time t along x-axis is given by x = 9t2 – t3 where x is in metres and t in second. What will be the position of this particle when it achieves maximum speed along the +ve x direction?

(a) 54 m (b) 81 m (c) 24 m (d) 32 m.

Ans: A

83. In a radioactive decay process, the negatively charged emitted β-particles are

(a) the electrons produced as a result of the decay of neutrons inside the nucleus

(b) the electrons produced as a result of collisions between atoms

(c) the electrons orbiting around the nucleus

(d) the electrons present inside the nucleus.

Ans: A

84. The phase difference between the instantaneous velocity and acceleration of a particle executing simple harmonic motion is

(a) π (b) 0.707π (c) zero (d) 0.5π

Ans: D

85. A wheel has angular acceleration of 3.0 rad/sec2 and an initial angular speed of 2.00 rad/sec. In a time of 2 sec it has rotated through an angle (in radian) of

(a) 10 (b) 12 (c) 4 (d) 6

Ans: A

86. A common emitter amplifier has a voltage gain of 50, an input impedance of 100Ω and an output impedance of 200Ω. The power gain of the amplifier is

(a) 1000 (b) 1250 (c) 100 (d) 500.

Ans: B

87. Three resistances P, Q, R each of 2Ω and an unknown resistance S form the four arms of a Wheatstone bridge circuit. When a resistance of 6Ω is connected in parallel to S the bridge gets balanced. What is the value of S?

(a) 3Ω (b) 6Ω (c) 1Ω (d) 2Ω

Ans: A

88. A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately

(a) 50% (b) 90% (c) 10% (d) 30%.

Ans: B

89. Two satellites of earth, S1 and S2 are moving in the same orbit. The mass of S1 is four times the mass of S2. Which one of the following statements is true?

(a) The potential energies of earth satellites in the two cases are equal. (b) S1 and S2 are moving with the same speed.

(c) The kinetic energies of the two satellites are equal. (d) The time period of S1 is four times that of S2.

Ans: B

90. The total energy of electron in the ground state of hydrogen atom is – 13.6 eV. The kinetic energy of an electron in the first excited state is

(a) 6.8 eV (b) 13.6 eV (c) 1.7 eV (d) 3.4 eV.

Ans: D

91. A 5 watt source emits monochromatic light of wavelength 5000 Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of

(a) 8 (b) 16 (c) 2 (d) 4

Ans: D

92. A particle executes simple harmonic oscillation with an amplitude a. The period of oscillation is T. The minimum time taken by the particle to travel half of the amplitude from the equilibrium position is

(a) T/8 (b) T/12 (c) T/2 (d) T/4

Ans: B

93. For a cubic crystal structure which one of the following relations indicating the cell characteristics is correct?

(a) a ≠ b ≠ c and α = β = γ = 90° (b) a = b = c and α ≠ β ≠ γ = 90°

(c) a = b = c and α = β = γ = 90° (c) a ≠ b ≠ c and α ≠ β and γ ≠ 90°

Ans: C

94. The resistance of an ammeter is 13 Ω and its scale is graduated for a current upto 100 amps. After an additional shunt has been connected to this ammeter it becomes possible to measure currents upto 750 amperes by this meter. The value of shunt-resistance is

(a) 2 Ω (b) 0.2 Ω (c) 2 k Ω (d) 20 Ω

Ans: A

95. An engine has an efficiency of 1/6. When the temperature os sink is reduced by 62°C, its efficiency is doubled. Temperature of the source is

(a) 37°C (b) 62°C (c) 99°C (d) 124°C

Ans: C

96. The electric and magnetic field of an electromagnetic wave are

(a) in opposite phase and perpendicular to each other

(b) in opposite phase and parallel to each other

(c) in phase and perpendicular to each other

(d) in phase and parallel to each other.

Ans: C

97. Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show

(a) anti ferromagnetism (b) no magnetic property

(c) diamagnetism (d) paramagnetism

Ans: D

98. Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion

(a) depends on both R and v (b) is independent of both R and v

(c) depends on R and not on v (d) depends on v and not on R

Ans: B

(a) 120 volts (b) 220 volts (c) 30 volts (d) 90 volts

Ans: A

81. A beam of electron passes undeflected through mutually perpendicular electric and magnetic fields. If the electric field is switched off, and the same magnetic field is maintained, the electrons move

(a) in a circular orbit (b) along a parabolic path

(c) along a straight line (d) in an elliptical orbit.

Ans: A

82. The position x of a particle with respect to time t along x-axis is given by x = 9t2 – t3 where x is in metres and t in second. What will be the position of this particle when it achieves maximum speed along the +ve x direction?

(a) 54 m (b) 81 m (c) 24 m (d) 32 m.

Ans: A

83. In a radioactive decay process, the negatively charged emitted β-particles are

(a) the electrons produced as a result of the decay of neutrons inside the nucleus

(b) the electrons produced as a result of collisions between atoms

(c) the electrons orbiting around the nucleus

(d) the electrons present inside the nucleus.

Ans: A

84. The phase difference between the instantaneous velocity and acceleration of a particle executing simple harmonic motion is

(a) π (b) 0.707π (c) zero (d) 0.5π

Ans: D

85. A wheel has angular acceleration of 3.0 rad/sec2 and an initial angular speed of 2.00 rad/sec. In a time of 2 sec it has rotated through an angle (in radian) of

(a) 10 (b) 12 (c) 4 (d) 6

Ans: A

86. A common emitter amplifier has a voltage gain of 50, an input impedance of 100Ω and an output impedance of 200Ω. The power gain of the amplifier is

(a) 1000 (b) 1250 (c) 100 (d) 500.

Ans: B

87. Three resistances P, Q, R each of 2Ω and an unknown resistance S form the four arms of a Wheatstone bridge circuit. When a resistance of 6Ω is connected in parallel to S the bridge gets balanced. What is the value of S?

(a) 3Ω (b) 6Ω (c) 1Ω (d) 2Ω

Ans: A

88. A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 amp, the efficiency of the transformer is approximately

(a) 50% (b) 90% (c) 10% (d) 30%.

Ans: B

89. Two satellites of earth, S1 and S2 are moving in the same orbit. The mass of S1 is four times the mass of S2. Which one of the following statements is true?

(a) The potential energies of earth satellites in the two cases are equal. (b) S1 and S2 are moving with the same speed.

(c) The kinetic energies of the two satellites are equal. (d) The time period of S1 is four times that of S2.

Ans: B

90. The total energy of electron in the ground state of hydrogen atom is – 13.6 eV. The kinetic energy of an electron in the first excited state is

(a) 6.8 eV (b) 13.6 eV (c) 1.7 eV (d) 3.4 eV.

Ans: D

91. A 5 watt source emits monochromatic light of wavelength 5000 Å. When placed 0.5 m away, it liberates photoelectrons from a photosensitive metallic surface. When the source is moved to a distance of 1.0 m, the number of photoelectrons liberated will be reduced by a factor of

(a) 8 (b) 16 (c) 2 (d) 4

Ans: D

92. A particle executes simple harmonic oscillation with an amplitude a. The period of oscillation is T. The minimum time taken by the particle to travel half of the amplitude from the equilibrium position is

(a) T/8 (b) T/12 (c) T/2 (d) T/4

Ans: B

93. For a cubic crystal structure which one of the following relations indicating the cell characteristics is correct?

(a) a ≠ b ≠ c and α = β = γ = 90° (b) a = b = c and α ≠ β ≠ γ = 90°

(c) a = b = c and α = β = γ = 90° (c) a ≠ b ≠ c and α ≠ β and γ ≠ 90°

Ans: C

94. The resistance of an ammeter is 13 Ω and its scale is graduated for a current upto 100 amps. After an additional shunt has been connected to this ammeter it becomes possible to measure currents upto 750 amperes by this meter. The value of shunt-resistance is

(a) 2 Ω (b) 0.2 Ω (c) 2 k Ω (d) 20 Ω

Ans: A

95. An engine has an efficiency of 1/6. When the temperature os sink is reduced by 62°C, its efficiency is doubled. Temperature of the source is

(a) 37°C (b) 62°C (c) 99°C (d) 124°C

Ans: C

96. The electric and magnetic field of an electromagnetic wave are

(a) in opposite phase and perpendicular to each other

(b) in opposite phase and parallel to each other

(c) in phase and perpendicular to each other

(d) in phase and parallel to each other.

Ans: C

97. Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond Curie temperature, then it will show

(a) anti ferromagnetism (b) no magnetic property

(c) diamagnetism (d) paramagnetism

Ans: D

98. Under the influence of a uniform magnetic field a charged particle is moving in a circle of radius R with constant speed v. The time period of the motion

(a) depends on both R and v (b) is independent of both R and v

(c) depends on R and not on v (d) depends on v and not on R

Ans: B

99. Which two of the following five physical parameters have the same dimensions?

(a) energy density (b) refractive index (c) dielectric constant (d) Young's modulus (e) magnetic field

(1) (a) and (e)

(2) (b) and (d)

(3) (c) and (e)

(4) (a) and (d)

Ans: 4

100. If the error in the measurement of radius of a sphere is 2%, then the error in the determination of volume of the sphere will be

(1) 2%

(2) 4%

(3) 6%

(4) 8%

Ans: 3

(a) energy density (b) refractive index (c) dielectric constant (d) Young's modulus (e) magnetic field

(1) (a) and (e)

(2) (b) and (d)

(3) (c) and (e)

(4) (a) and (d)

Ans: 4

100. If the error in the measurement of radius of a sphere is 2%, then the error in the determination of volume of the sphere will be

(1) 2%

(2) 4%

(3) 6%

(4) 8%

Ans: 3