UP PGT 2021 — Physics (Series A)

Physics

1. 1. Identify the incorrect statement.

   • (a) Radioactivity makes it possible to establish the age of many geological and biological specimens.
   • (b) Radiocarbon is the beta-active carbon isotope ¹⁴₆C.
   • (c) Living plants and animals have different ratio of radiocarbon to ordinary carbon.
   • (d) Cosmic rays are high energy atomic nuclei chiefly protons.
   उत्तर देखें

   उत्तर: (c)

2. 2. The dynamic plate resistance r_p, mutual conductance g_m and amplification factor μ of a triode valve are related to each other as

   • (a) r_p = μ.g_m
   • (b) g_m = μ.r_p
   • (c) μ = r_p.g_m
   • (d) r_p² = μ² + g_m²
   उत्तर देखें

   उत्तर: (c)

3. 3. The displacement equation of oscillations of a particle executing simple harmonic motion is x = 5 sin(0.2πt + 0.5π) The time period of particle is

   • (a) 10.0 s
   • (b) 1.0 s
   • (c) 0.8 s
   • (d) 0.5 s
   उत्तर देखें

   उत्तर: (a)

4. 4. A car moving at 30 m/s is approaching a factory, whose whistle has a frequency of 500 Hz. If the speed of sound in air is 340 m/s, what is the apparent frequency of whistle as heard by the car driver ?

   • (a) 480 Hz
   • (b) 500 Hz
   • (c) 544 Hz
   • (d) 600 Hz
   उत्तर देखें

   उत्तर: (c)

5. 5. The Kinetic energy per unit volume of a perfect gas is equal to Where P is pressure.

   • (a) (2/3)P
   • (b) (3/2)P
   • (c) P/3
   • (d) (1/2)P
   उत्तर देखें

   उत्तर: (b)

6. 6. Anderson’s Bridge is used for measurement of

   • (a) Capacitance
   • (b) Self-inductance
   • (c) Resistance
   • (d) Frequency of AC supply
   उत्तर देखें

   उत्तर: (b)

7. 7. Newton’s law of cooling is a special case of

   • (a) Stefan’s law
   • (b) Kirchhoff’s law
   • (c) Planck’s law
   • (d) Wien’s displacement law
   उत्तर देखें

   उत्तर: (a)

8. 8. A block of steel heated to 100° C is left in a room to cool. Which of the curves shown in figure, represents the correct behaviour ?

   • (a) A
   • (b) B
   • (c) C
   • (d) None
   उत्तर देखें

   उत्तर: (a)

9. 9. The wavelength of k_α x-ray line of an element of atomic number z = 11 is λ. The wavelength of k_α x-ray line of another element of atomic number z is 4λ. Then z is

   • (a) 11
   • (b) 44
   • (c) 6
   • (d) 4
   उत्तर देखें

   उत्तर: (c)

10. 10. An electrical heater is labeled 1500 W/220 V. How much current does this heater draw from a 220 V source ?

    • (a) 5.1 A
    • (b) 6.8 A
    • (c) 9.2 A
    • (d) 10.0 A
    उत्तर देखें

    उत्तर: (b)

11. 11. For a van der Waals gas the inversion temperature at low pressure is

    • (a) 27a/(bR)
    • (b) a/(8Rb)
    • (c) ab/(8R)
    • (d) 2a/(Rb)
    उत्तर देखें

    उत्तर: (d)

12. 12. Infinite equal charges q are placed along a line at distances 1 meter, 2 meter, 4 meter, 16 meter, 32 meter and so on. Potential due to all charges are

    • (a) Zero
    • (b) q/(4π∈₀)
    • (c) q/(2π∈₀)
    • (d) q/(8π∈₀)
    उत्तर देखें

    उत्तर: —

13. 13. Eight equal drops of water are falling through air with a steady velocity of 5 cm/sec. If the drops coalesce, what will be the new terminal velocity ?

    • (a) 5 cm/s
    • (b) 10 cm/s
    • (c) 20 cm/s
    • (d) 40 cm/s
    उत्तर देखें

    उत्तर: (c)

14. 14. The length of an object is measured as 1.526 m. Taking significant figures into account, the absolute error, relative error and percentage error are

    • (a) 0.0001 m, 0.000065, 0.065%
    • (b) 0.001 m, 0.00065, 0.065%
    • (c) 0.001 m, 0.001, 0.1%
    • (d) 0.0001 m, 0.0001, 0.1%
    उत्तर देखें

    उत्तर: (b)

15. 15. When the plate voltage applied to a diode valve is changed from 48 V to 50 V, the plate current increases from 60 mA to 70 mA. What is the dynamic plate resistance of the diode ?

    • (a) 200 Ω
    • (b) 180 Ω
    • (c) 150 Ω
    • (d) 120 Ω
    उत्तर देखें

    उत्तर: (a)

16. 16. Two thin lenses, of focal lengths +15 cm and −12 cm, are placed in contact. The focal length of the combination lens will be

    • (a) + 3 cm
    • (b) + 15 cm
    • (c) − 12 cm
    • (d) − 60 cm
    उत्तर देखें

    उत्तर: (d)

17. 17. The critical angle is maximum when light travels from

    • (a) water to air
    • (b) glass to air
    • (c) glass to water
    • (d) air to water
    उत्तर देखें

    उत्तर: (c)

18. 18. The ratio of masses of a pion and an electron is about

    • (a) 270
    • (b) 50
    • (c) 20
    • (d) 5
    उत्तर देखें

    उत्तर: (a)

19. 19. At what temperature of a body, the Fahrenheit and Kelvin thermometer scales give equal numerical values ?

    • (a) 40°
    • (b) 180°
    • (c) 435°
    • (d) 574°
    उत्तर देखें

    उत्तर: (d)

20. 20. Fibre optics works on the principle of

    • (a) Snell’s law
    • (b) Total internal reflection
    • (c) (A) and (B) both
    • (d) Population inversion
    उत्तर देखें

    उत्तर: (b)

21. 21. Which of the following is path dependent ? Where U = Internal Energy P = Pressure V = Volume

    • (a) U
    • (b) PdV
    • (c) P
    • (d) V
    उत्तर देखें

    उत्तर: (b)

22. 22. What is the potential difference between the centre and the surface of a sphere of radius R with uniform charge density e within it ?

    • (a) eR²/(3∈₀)
    • (b) eR²/(6∈₀)
    • (c) eR²/(2∈₀)
    • (d) zero
    उत्तर देखें

    उत्तर: (b)

23. 23. For a given material the value of Young’s modulus (Y) is 2.4 times of its modulus of rigidity (η), the value of Poisson’s ratio of the material is

    • (a) 2.4
    • (b) 1.2
    • (c) 0.4
    • (d) 0.2
    उत्तर देखें

    उत्तर: (d)

24. 24. Which of the following circuit is being used in impedance matching ?

    • (a) transistor in common base configuration
    • (b) transistor in common emitter configuration
    • (c) transistor in common collector configuration
    • (d) zener diode in reverse bias
    उत्तर देखें

    उत्तर: (c)

25. 25. A satellite is revolving round the earth at a height of 600 km from the surface of earth. The speed of the satellite is (Radius of the earth = 6400 km, mass of the earth : 6 × 10²⁴ kg. G = 6.67 × 10⁻¹¹ N-m²/kg²)

    • (a) 11.00 km/s
    • (b) 9.00 km/s
    • (c) 7.60 km/s
    • (d) 4.92 km/s
    उत्तर देखें

    उत्तर: (c)

26. 26. For μ_o = 1.544, μ_E = 1.558 and λ = 6500 Å, the thickness of a quarter wave plate is Here notations carry their usual meaning.

    • (a) 10.0 μm
    • (b) 11.6 μm
    • (c) 0.25 μm
    • (d) 0.28 μm
    उत्तर देखें

    उत्तर: (b)

27. 27. Kirchhoff’s Laws are applicable to

    • (a) DC only
    • (b) AC only
    • (c) AC and DC both
    • (d) None of the above
    उत्तर देखें

    उत्तर: (c)

28. 28. If 25% of a radioactive material decays in 5 years, how much of the original material will be left undecayed after 20 years ?

    • (a) 5%
    • (b) 10%
    • (c) 25%
    • (d) 32%
    उत्तर देखें

    उत्तर: (d)

29. 29. A dipole is formed by two charges of 5μC and −5μC at a distance of 8 mm. Find electric field at i) a point 25 cm away from dipole centre at its axis and ii) a point 20 cm away on a line perpendicular to the axis and passing through its centre

    • (a) 6 × 10⁶ N/C, 4.5 × 10⁴ N/C
    • (b) 4.6 × 10⁴ N/C, 4.5 × 10⁴ N/C
    • (c) − 4.6 × 10⁴ N/C, 4.5 × 10⁴ N/C
    • (d) 4.5 × 10⁴ N/C, 6 × 10⁶ N/C
    उत्तर देखें

    उत्तर: (c)

30. 30. In a driven series LCR circuit, the resonant frequency f_r is given by

    • (a) f_r = 1/(2π√(LC))
    • (b) f_r = 2π√(LC)
    • (c) f_r = 2π√(L/C)
    • (d) f_r = 2π√(C/L)
    उत्तर देखें

    उत्तर: (a)

31. 31. At constant pressure the temperature of gas T, at which root−mean−square velocity is twice its value at 0°C, is

    • (a) 819° K
    • (b) 900° K
    • (c) 980° K
    • (d) 819° C
    उत्तर देखें

    उत्तर: (d)

32. 32. A galvanometer has a resistance of 80 Ω and deflects full scale for a potential of 20 mV across it. How large a series resistance is required to convert it to a 5V voltmeter ?

    • (a) 4920 Ω
    • (b) 5220 Ω
    • (c) 10520 Ω
    • (d) 19920 Ω
    उत्तर देखें

    उत्तर: (d)

33. 33. A Carnot cycle is represented on an entropy-temperature diagram by which one of the following figures ?

    • (a)
    • (b)
    • (c)
    • (d)
    उत्तर देखें

    उत्तर: (b)

34. 34. The mean Kinetic energy of one mole of gas per degree of freedom (on the basis of Kinetic theory of gases) is

    • (a) (1/2)KT
    • (b) (3/2)KT
    • (c) (3/2)RT
    • (d) (1/2)RT
    उत्तर देखें

    उत्तर: (d)

35. 35. In central force motion which one of the following physical quantity is conserved ?

    • (a) Angular momentum
    • (b) Kinetic energy
    • (c) Linear momentum
    • (d) Total energy
    उत्तर देखें

    उत्तर: (a)

36. 36. The best filter used in a power supply is

    • (a) L – section filter
    • (b) Capacitor input filter
    • (c) Choke input filter
    • (d) π – section filter
    उत्तर देखें

    उत्तर: (d)

37. 37. Viscosity of a gas is due to transport of

    • (a) momentum
    • (b) energy
    • (c) mass
    • (d) none of these
    उत्तर देखें

    उत्तर: (a)

38. 38. The gain in potential energy of an object of mass m raised from the surface of earth to a height equal to the radius R of the earth, is (g = acceleration due to gravity at the earth’s surface).

    • (a) (3/2)mgR
    • (b) (1/2)mgR
    • (c) (2/3)mgR
    • (d) mgR
    उत्तर देखें

    उत्तर: (b)

39. 39. The peak voltage in a 240V A.C. source is

    • (a) 240 V
    • (b) 300 V
    • (c) 340 V
    • (d) 380 V
    उत्तर देखें

    उत्तर: (c)

40. 40. Two coherent sources of intensity ratio 100 : 1 interfere. The ratio of intensity between maxima and minima is

    • (a) 100 : 1
    • (b) 10 : 1
    • (c) 11 : 9
    • (d) 121 : 81
    उत्तर देखें

    उत्तर: (d)

41. 41. In a Young’s double slit experiment the slit separation is 0.12 mm, the wavelength of light used is 5893 A° and interference pattern is observed on a screen 1m away. The separation between successive bright fringes will be

    • (a) 6.50 mm
    • (b) 5.50 mm
    • (c) 4.91 mm
    • (d) 4.50 mm
    उत्तर देखें

    उत्तर: (c)

42. 42. An achromatic combination of two thin lenses of focal lengths f₁ and f₂, is achieved if separation between them is equal to

    • (a) f₁/2
    • (b) (1/2)(f₁ + f₂)
    • (c) f₂/2
    • (d) (1/2)(f₁ − f₂)
    उत्तर देखें

    उत्तर: (b)

43. 43. The mean separation of two points on moon that can be resolved by a 500 cm telescope aperture is (distance of the moon is 4 × 10⁵ km, eye is most sensitive to wavelength 5500 Å)

    • (a) 40 m
    • (b) 43 m
    • (c) 53.6 m
    • (d) 50.6 m
    उत्तर देखें

    उत्तर: (c)

44. 44. The light from the sun has maximum intensity for the wavelength of 470 nm. Assuming that the surface of the sun emits as a blackbody, calculate the temperature of the sun. (Wien’s constant = 0.288 cm. °K)

    • (a) 8000°K
    • (b) 7000°K
    • (c) 6128°K
    • (d) 5000°K
    उत्तर देखें

    उत्तर: (c)

45. 45. Two Nicols are crossed to each other. Now, one of them is rotated through 30°. What percentage of incident polarised light will pass through the system ?

    • (a) 100%
    • (b) 75%
    • (c) 25%
    • (d) 12.5%
    उत्तर देखें

    उत्तर: —

46. 46. The process of changing a weak signal without altering its shape into a strong one is known as

    • (a) Biasing
    • (b) Rectification
    • (c) Modulation
    • (d) Amplification
    उत्तर देखें

    उत्तर: (d)

47. 47. The potential energy U(x) of a particle executing S.H.M. is

    • (a) U(x) = constant
    • (b) U(x) = Ae^(−bx)
    • (c) U(x) = (1/2)K(x − a)²
    • (d) U(x) = K₁x + K₂x²
    उत्तर देखें

    उत्तर: (c)

48. 48. The magnetic susceptibility χ of a material varies with absolute temperature T as χ = C/T where C is a constant. This material is

    • (a) paramagnetic
    • (b) diamagnetic
    • (c) ferromagnetic
    • (d) ferrimagnetic
    उत्तर देखें

    उत्तर: (a)

49. 49. Thermal conductivity of bad conductors is measured by

    • (a) Searle’s method
    • (b) Lee’s disc method
    • (c) Callendar and Barne’s method
    • (d) None of the above
    उत्तर देखें

    उत्तर: (b)

50. 50. In the following circuit if between point A and B, a potential of 100 volt is established, then find value of charge of the nearest capacitor to point A.

    • (a) 100 μC
    • (b) 300 μC
    • (c) 150 μC
    • (d) 200 μC
    उत्तर देखें

    उत्तर: —

51. 51. 0.0314 cm³ of a liquid is flowing out per second through a capillary tube of 1 mm radius. Velocity of the liquid at a point on the axis of the capillary is

    • (a) 2 cm/s
    • (b) 1.5 cm/s
    • (c) 1 cm/s
    • (d) 0
    उत्तर देखें

    उत्तर: (a)

52. 52. The average value of I from t = 0 to t = T, for I = I₀sin²ωt where ω = 2π/T, is

    • (a) 2I₀
    • (b) 3I₀
    • (c) I₀/2
    • (d) I₀/3
    उत्तर देखें

    उत्तर: (c)

53. 53. Mark the wrong statement.

    • (a) The characteristic X-ray spectrum consists of sharp peaks superimposed on the continuous spectrum.
    • (b) The characteristic X-rays from substances of higher atomic number are of longer wavelength than those from lower atomic number.
    • (c) X-rays from higher atomic number are more penetrating.
    • (d) Characteristic X-rays are generated when an electron from a higher inner shell jumps to lower.
    उत्तर देखें

    उत्तर: (b)

54. 54. The current in an AC circuit is wattless when the phase difference between current and voltage is

    • (a) zero
    • (b) π/4
    • (c) π/2
    • (d) π
    उत्तर देखें

    उत्तर: (c)

55. 55. The mean free path of molecules of a certain gas at pressure p and temperature T is 2 × 10⁻⁷ m. The mean free path for the same gas at pressure p/2 and temperature 2T, will be

    • (a) 10 × 10⁻⁷ m
    • (b) 8 × 10⁻⁷ m
    • (c) 6 × 10⁻⁷ m
    • (d) 4 × 10⁻⁷ m
    उत्तर देखें

    उत्तर: (b)

56. 56. Two waves y₁ = A₁ sin k(x − υt) and y₂ = A₂ sin k(x − υt + x₀), where k = 2π cm⁻¹ and x₀ = 1.50 cm are superposed. If A₁ = 9.00 mm and A₂ = 7.00 mm, what is the amplitude of the resulting wave ?

    • (a) 16.0 mm
    • (b) 8.0 mm
    • (c) 2.0 mm
    • (d) 1.0 mm
    उत्तर देखें

    उत्तर: (c)

57. 57. The function of a detector is to demodulate the modulated carrier wave and the steps for the process are

    • (a) Demodulation and filtering
    • (b) Demodulation and rectification
    • (c) Rectification and filtering
    • (d) Generation and filtering
    उत्तर देखें

    उत्तर: (c)

58. 58. An air core solenoid with 2000 loops in it, is 60 cm long and has a diameter of 2 cm. If a current of 5A is sent through it, the flux density within it will be

    • (a) 0.042 T
    • (b) 0.035 T
    • (c) 0.030 T
    • (d) 0.021 T
    उत्तर देखें

    उत्तर: (d)

59. 59. Consider a solid cylinder of mass M and radius R rolling down an inclined plane without slipping from a height h. The speed of its centre of mass when the cylinder reaches the bottom, is

    • (a) √((4/3)gh)
    • (b) √(2gh)
    • (c) √((3/2)gh)
    • (d) √((3/5)gh)
    उत्तर देखें

    उत्तर: (a)

60. 60. Two charges q₁ and q₂ are placed close to each other, if a third charge q₃ is brought near to it, the force now exerted by q₁ on q₂

    • (a) increases
    • (b) decreases
    • (c) remains the same
    • (d) reduces to zero
    उत्तर देखें

    उत्तर: (c)

61. 61. The greatest length of a wire that can be stretched without breaking. (Given breaking stress = 7.2 × 10⁸ N/m², density of wire = 7.8 × 10³ kg/m³)

    • (a) 10 metre
    • (b) 9.4 metre
    • (c) 9.4 kilometre
    • (d) 100 metre
    उत्तर देखें

    उत्तर: (c)

62. 62. The elementary particles responsible for holding nucleons together to form atomic nuclei are

    • (a) Gluons
    • (b) Mesons
    • (c) Bosons
    • (d) Neutrinos
    उत्तर देखें

    उत्तर: (b)

63. 63. Which of the following is a reversible process ?

    • (a) Production of heat by the passage of current through an electrical resistance
    • (b) Conduction of heat from a hot body to a colder body
    • (c) The changes in the pressure and volume of the working substance takes place at infinitely slow rate
    • (d) Forcing of a real gas or liquid through a valve or porous plug while keeping them insulated with the environment
    उत्तर देखें

    उत्तर: (c)

64. 64. The source of solar energy is

    • (a) burning of hydrogen
    • (b) nuclear fission reactions
    • (c) nuclear fusion reactions
    • (d) radiant energy received from other solar systems
    उत्तर देखें

    उत्तर: (c)

65. 65. What is the capacitance of the earth if it is assumed to be a spherical conductor of radius 6400 Km ?

    • (a) 711 μF
    • (b) 640 μF
    • (c) 900 μF
    • (d) 1406 F
    उत्तर देखें

    उत्तर: (a)

66. 66. A spherical body with radius 12 cm radiates 450 W power at 500 K. If the radius were halved and the temperature doubled, what would be the power radiated ?

    • (a) 900 W
    • (b) 7200 W
    • (c) 3600 W
    • (d) 1800 W
    उत्तर देखें

    उत्तर: (d)

67. 67. The ratio of most probable speed and average speed of a gas enclosed in a vessel is

    • (a) √π/4
    • (b) 1
    • (c) √π/2
    • (d) 2/√π
    उत्तर देखें

    उत्तर: (c)

68. 68. The mean free path of thermal neutrons in ¹¹³Cd is (Given : nσ = 1.12 × 10⁴ m⁻¹, n → number of atoms per cubic metre, σ → capture cross section)

    • (a) 0.2678 mm
    • (b) 0.1786 mm
    • (c) 0.0892 mm
    • (d) 0.1339 mm
    उत्तर देखें

    उत्तर: (c)

69. 69. Maximum rectification efficiency of a half-wave rectifier is

    • (a) 40.6%
    • (b) 50.0%
    • (c) 81.2%
    • (d) 100.0%
    उत्तर देखें

    उत्तर: (a)

70. 70. For incidence at Brewster’s angle, the angle between reflected and refracted rays, is

    • (a) 120°
    • (b) 90°
    • (c) 70°
    • (d) 60°
    उत्तर देखें

    उत्तर: (b)

71. 71. An object of mass M moving with velocity v explodes and breaks up into three equal pieces. Immediately after the explosion two pieces become stationary, but the third piece keeps moving. What is the kinetic energy of this piece ?

    • (a) 2 Mv²
    • (b) (3/2)Mv²
    • (c) Mv²
    • (d) (1/2)Mv²
    उत्तर देखें

    उत्तर: (b)

72. 72. The streamline flow of an incompressible and non-viscous liquid is described by

    • (a) Boyle’s law
    • (b) Poiseuille’s law
    • (c) Archimedes principle
    • (d) Bernoulli’s principle
    उत्तर देखें

    उत्तर: (d)

73. 73. The flux of the electric field strength through each of the faces of a closed cube of edge length l, if a charge q is placed at its centre, is

    • (a) q/(6∈₀l²)
    • (b) q/(6∈₀l)
    • (c) q/(6∈₀)
    • (d) q/(6∈₀l³)
    उत्तर देखें

    उत्तर: (c)

74. 74. 20 μA current is flowing in a wire for 30 seconds. The number of electrons passing through wire is

    • (a) 375 × 10¹³
    • (b) 375 × 10¹⁵
    • (c) 375 × 10¹⁶
    • (d) 375 × 10¹⁷
    उत्तर देखें

    उत्तर: (a)

75. 75. A cube of aluminium of side 10 cm is subjected to a shearing force of 100 N. The top surface of the cube is displaced by 0.01 cm with respect to bottom. The value of modulus of rigidity is

    • (a) 10⁴ N/m²
    • (b) 10³ N/m²
    • (c) 10⁷ N/m²
    • (d) 10⁻⁵ N/m²
    उत्तर देखें

    उत्तर: (c)

76. 76. A coil having inductance 0.15 H and resistance 15Ω is connected across a 220 V, 50 Hz line. Compute the current in the coil.

    • (a) 4.45 A
    • (b) 4.25 A
    • (c) 4.00 A
    • (d) 3.50 A
    उत्तर देखें

    उत्तर: (a)

77. 77. Two interfering waves have intensities in the ratio 9 : 1. The ratio of maximum and minimum intensities, in interference pattern, will be

    • (a) 5 : 4
    • (b) 2 : 1
    • (c) 25 : 16
    • (d) 4 : 1
    उत्तर देखें

    उत्तर: (d)

78. 78. The internal radius of a 1 m long resonance tube is 3 cm. With a tuning fork of frequency 2000 Hz, the first resonating position is 4.6 cm and the second resonating position is 14.0 cm. Speed of sound at the room temperature is

    • (a) 336 m/s
    • (b) 376 m/s
    • (c) 332 m/s
    • (d) 340 m/s
    उत्तर देखें

    उत्तर: (b)

79. 79. The efficiency of a Carnot engine is 25%. If the temperature of its source is 327°C, the temperature of the sink must be

    • (a) 82°C
    • (b) 127°C
    • (c) 177°C
    • (d) 227°C
    उत्तर देखें

    उत्तर: (c)

80. 80. A driven (forced) harmonic oscillator has settled down to a steady state of oscillation. In steady state, the ratio of average power absorbed and average power dissipated will be

    • (a) 1/3
    • (b) 1/2
    • (c) 1
    • (d) 2
    उत्तर देखें

    उत्तर: (c)

81. 81. The value of grad (1/r) is

    • (a) − r⃗/r
    • (b) zero
    • (c) − r⃗/r³
    • (d) − r⃗/r²
    उत्तर देखें

    उत्तर: (c)

82. 82. The electric potential due to dipole p, at a point distant r from it and in the direction θ from the dipoles is

    • (a) (1/(4π∈₀)) (p cosθ/r²)
    • (b) (1/(4π∈₀)) (p/r³)
    • (c) (1/(4π∈₀)) (p sinθ/r²)
    • (d) (1/(4π∈₀)) (p tanθ/r²)
    उत्तर देखें

    उत्तर: (a)

83. 83. The radius of the orbit of a satellite is 16 times the radius of the orbit of a geo-stationary satellite. The period of the satellite is

    • (a) 4 days
    • (b) 16 days
    • (c) 64 days
    • (d) 96 days
    उत्तर देखें

    उत्तर: (c)

84. 84. J⃗ = σE⃗, where J is current density, σ is conductivity and E is electric field, is

    • (a) Maxwell’s equation
    • (b) Continuity equation
    • (c) Ampere’s law
    • (d) A form of Ohm’s law
    उत्तर देखें

    उत्तर: (d)

85. 85. A rectangular glass plate of refractive index 1.5 is used as a polarizer. The corresponding polarizing angle will be

    • (a) 43.7°
    • (b) 33.7°
    • (c) 56.3°
    • (d) 23.4°
    उत्तर देखें

    उत्तर: (c)

86. 86. Planck’s radiation law reduces to Wien’s law for

    • (a) higher λ
    • (b) lower λ
    • (c) higher temperature
    • (d) lower temperature
    उत्तर देखें

    उत्तर: (b)

87. 87. The displacement current arises due to

    • (a) positive charges only
    • (b) negative charges only
    • (c) both positive and negative charges
    • (d) time varying electric field
    उत्तर देखें

    उत्तर: (d)

88. 88. Two lenses have dispersive powers in ratio 2 : 3. These glasses are used to make achromatic lens of focal length 20 cm. The value of focal lengths of two lenses are

    • (a) f₁ = 5 cm, f₂ = − 10 cm
    • (b) f₁ = −10 cm, f₂ = 10 cm
    • (c) f₁ = 6.67 cm, f₂ = − 10 cm
    • (d) f₁ = 10 cm, f₂ = − 10 cm
    उत्तर देखें

    उत्तर: (c)

89. 89. If the resultant R⃗ of two vectors P⃗ and Q⃗ is such that R² = P² + Q², the angle between vector P⃗ and Q⃗ is

    • (a) zero
    • (b) 45°
    • (c) 60°
    • (d) 90°
    उत्तर देखें

    उत्तर: (d)

90. 90. The equivalent capacitance of the combination shown in figure below, is

    • (a) 3C
    • (b) 2C
    • (c) C
    • (d) C/2
    उत्तर देखें

    उत्तर: (b)

91. 91. Torsional couple required to twist a cylinder of length L/2, radius r and modulus of rigidity η by one turn will be

    • (a) 2π²ηr⁴/L
    • (b) πηr⁴/(2L)
    • (c) π²ηr⁴/L
    • (d) 360πηr⁴/L
    उत्तर देखें

    उत्तर: (a)

92. 92. The photoelectric threshold wavelength for a metal is 3000 Å. What is the kinetic energy of an electron ejected from it by radiation of wavelength 1200 Å ?

    • (a) 6.2 eV
    • (b) 3.1 eV
    • (c) 1.65 eV
    • (d) 1.03 eV
    उत्तर देखें

    उत्तर: —

93. 93. If 1.20 V potential difference must be applied to stop the fastest photoelectrons emitted by a nickel surface under the action of ultraviolet light of wavelength 2000 Å, calculate the work function of nickel.

    • (a) 6.21 eV
    • (b) 5.01 eV
    • (c) 4.80 eV
    • (d) 4.50 eV
    उत्तर देखें

    उत्तर: (b)

94. 94. A half-wave plate produces a phase difference between O (ordinary) and E (extraordinary) waves equal to

    • (a) π/2
    • (b) 3π/2
    • (c) π
    • (d) π/4
    उत्तर देखें

    उत्तर: (c)

95. 95. Which one of the following is used as a coolant/moderator in a nuclear reactor ?

    • (a) Distilled water
    • (b) Fresh water
    • (c) Heavy water
    • (d) Ice
    उत्तर देखें

    उत्तर: (c)

96. 96. A water drop of radius 10⁻² m is broken into 1000 equal droplets. If the surface tension of water is 0.075 N/m, the gain in surface energy will be

    • (a) 8.5 × 10⁻⁴ J
    • (b) 8.1 × 10⁻⁴ J
    • (c) 7.7 × 10⁻⁴ J
    • (d) 7.5 × 10⁻⁴ J
    उत्तर देखें

    उत्तर: (a)

97. 97. The average binding energy per nucleon of most nuclei is of the order of

    • (a) 10⁻¹² eV
    • (b) 10⁻¹² MeV
    • (c) 10⁻¹² BeV
    • (d) 10⁻¹² J
    उत्तर देखें

    उत्तर: (d)

98. 98. The numerical aperture of a microscope is given by

    • (a) μ/sin i
    • (b) μ sin i
    • (c) sin i/μ
    • (d) sin⁻¹ i/μ
    उत्तर देखें

    उत्तर: (b)

99. 99. A tuning fork of frequency 260 Hz is vibrated with a sonometer wire and 5 beats are heard. If the tension in the wire is slightly increased, the beat frequency also increases. The original frequency of the sonometer is

    • (a) 265 Hz
    • (b) 260 Hz
    • (c) 255 Hz
    • (d) 250 Hz
    उत्तर देखें

    उत्तर: (a)

100. 100. If r₀ is the radius of the first (n = 1) Bohr orbit in a hydrogen atom, the radius of the fourth (n = 4) orbit is given by

     • (a) 16 r₀
     • (b) 4r₀
     • (c) (1/4)r₀
     • (d) (1/16)r₀
     उत्तर देखें

     उत्तर: (a)

101. 101. An adiabatic process is also known as

     • (a) isothermal
     • (b) isobaric
     • (c) isoentropic
     • (d) isochoric
     उत्तर देखें

     उत्तर: (c)

102. 102. An iron plate 2 cm thick has a cross-section of 5000 cm². Its one side is at 110°C and the other side is at 100°C. If thermal conductivity of iron is 0.115 cal/s-cm-°C, the rate of heat flow through the plate is

     • (a) 5750 cal/s
     • (b) 4750 cal/s
     • (c) 2875 cal/s
     • (d) 2375 cal/s
     उत्तर देखें

     उत्तर: (c)

103. 103. Sunlight is reflected from a lake is 100% polarized at any instant. The angle between the sun and horizon at that instant is (Given tan⁻¹(1.33) = 53.06°, μ of water = 1.33)

     • (a) 53.06°
     • (b) 36°54′
     • (c) 143.06°
     • (d) 126°54′
     उत्तर देखें

     उत्तर: (c)

104. 104. At the peak of the nuclear binding energy curve

     • (a) Z is even but N is odd
     • (b) Z is odd but N is even
     • (c) Both Z and N are odd
     • (d) Both Z and N are even
     उत्तर देखें

     उत्तर: (d)

105. 105. When a small solid sphere is dropped in a viscous liquid, it finally acquires a uniform velocity which is called

     • (a) Escape velocity
     • (b) Terminal velocity
     • (c) Critical velocity
     • (d) Reynold velocity
     उत्तर देखें

     उत्तर: (b)

106. 106. The instrument used to measure optical rotation is known as

     • (a) spectrometer
     • (b) microscope
     • (c) polarimeter
     • (d) interferometer
     उत्तर देखें

     उत्तर: (c)

107. 107. If the focal length of objective lens is increased then magnifying power of

     • (a) microscope will increase but that of telescope decrease
     • (b) microscope and telescope both will increase
     • (c) microscope and telescope both will decrease
     • (d) microscope will decrease but that of telescope will increase
     उत्तर देखें

     उत्तर: (d)

108. 108. A capacitor with air between its plates has a capacitance of 8 μF. Its capacitance on introducing a dielectric with dielectric constant 6 between its plates, is

     • (a) 48 μF
     • (b) 40 μF
     • (c) 32 μF
     • (d) 16 μF
     उत्तर देखें

     उत्तर: (a)

109. 109. The gravitational field due to a mass distribution is given by E = kx^(−3/2) in x-direction, where k is a positive constant. Taking gravitational potential to be zero at infinity, its value at a distance x is

     • (a) 2k√x
     • (b) 2k/√x
     • (c) 2kx³
     • (d) 2k/x³
     उत्तर देखें

     उत्तर: (b)

110. 110. Potential energy per unit volume u of a strained wire is

     • (a) u = stress × strain
     • (b) u = (1/4) stress × strain
     • (c) u = (1/2) stress × strain
     • (d) u = (3/4) stress × strain
     उत्तर देखें

     उत्तर: (c)

111. 111. A Carnot engine is working between 127°C and 27°C. It absorbs 80 cals of heat. How much heat is rejected ?

     • (a) 80 cals
     • (b) 60 cals
     • (c) 40 cals
     • (d) 20 cals
     उत्तर देखें

     उत्तर: (b)

112. 112. State of population inversion in LASER is

     • (a) an equilibrium state and number of atoms in ground state is more than that of excited state
     • (b) a non equilibrium state and number of atoms in ground state is less than that of in excited state
     • (c) an equilibrium state and number of atoms in ground state is same as that in excited states
     • (d) a non equilibrium state and number of all atoms lie in excited state
     उत्तर देखें

     उत्तर: (b)

113. 113. Compute the magnetic induction in air at a point 10 cm from a long straight wire carrying a current of 20 A.

     • (a) 3 × 10⁻⁵ T
     • (b) 4 × 10⁻⁵ T
     • (c) 5 × 10⁻⁵ T
     • (d) 6 × 10⁻⁵ T
     उत्तर देखें

     उत्तर: (b)

114. 114. When the current in a coil changes from 8A to 2A in 3 × 10⁻³s, the emf induced in the coil is 2V. The self inductance of the coil is

     • (a) 1 mH
     • (b) 5 mH
     • (c) 20 mH
     • (d) 10 mH
     उत्तर देखें

     उत्तर: (a)

115. 115. A 200 mm long polarimeter tube containing 48 cm³ of sugar solution produces an optical rotation of 11° when placed in a polarimeter and infront of white light, if the specific rotation of sugar solution is 66°. The amount of sugar contained in the tube in form of solution is

     • (a) 5 gm
     • (b) 10 gm
     • (c) 2 gm
     • (d) 4 gm
     उत्तर देखें

     उत्तर: (d)

116. 116. 4 equal point charges, +4μC, are placed at four corners of a square that is 50 cm on a side. The force on any of the charges, is

     • (a) 1.10 N inward along diagonal
     • (b) 0.72 N inward along diagonal
     • (c) 0.72 N outward along diagonal
     • (d) 1.10 N outward along diagonal
     उत्तर देखें

     उत्तर: (d)

117. 117. According to Planck the average energy of oscillators with frequency υ and its integral multiples is

     • (a) kT
     • (b) hυ exp(−hυ/kT)
     • (c) hυ / [exp(−hυ/kT) + 1]
     • (d) hυ / [exp(−hυ/kT) − 1]
     उत्तर देखें

     उत्तर: —

118. 118. The differential equation of three dimensional wave is

     • (a) ∇⃗²Ψ = (1/υ²) ∂²Ψ/∂t²
     • (b) Ψ(r⃗, t) = A₀ sin(ωt − k⃗.r⃗)
     • (c) ∂²Ψ/∂t² = υ² ∂Ψ/∂x
     • (d) ∇⃗Ψ = υ² ∂Ψ/∂t
     उत्तर देखें

     उत्तर: (a)

119. 119. Minimum energy required for electron-positron pair production is

     • (a) 0.5 MeV
     • (b) 1 KeV
     • (c) 0.5 KeV
     • (d) 1 MeV
     उत्तर देखें

     उत्तर: (d)

120. 120. The magnetic susceptibility of a diamagnetic material is

     • (a) small and negative
     • (b) small and positive
     • (c) large and positive
     • (d) large and negative
     उत्तर देखें

     उत्तर: (a)

121. 121. The sensitivity of a Wheatstone bridge is maximum when

     • (a) P/Q = R/X
     • (b) P = Q, R = X
     • (c) P = Q = R = X
     • (d) None of these
     उत्तर देखें

     उत्तर: (c)

122. 122. 20 grams of ice at 0°C melts to water at 0°C. The entropy change in this process, is (Latent heat of water is 80 cal/gm)

     • (a) 24.5 J/°K
     • (b) 30.2 J/°K
     • (c) 35.7 J/°K
     • (d) 49.2 J/°K
     उत्तर देखें

     उत्तर: (a)

123. 123. The shape of the Lissajous Figures depends on

     • (a) The amplitude of the superposing waves
     • (b) Frequencies of superposing waves
     • (c) The phase difference between the superposing waves
     • (d) All of the above
     उत्तर देखें

     उत्तर: (d)

124. 124. When a linear load W is applied to a metal wire of length l, its length increases by Δl. The fractional change in its volume ΔV/V will be proportional to

     • (a) √(Δl/l)
     • (b) (Δl/l)²
     • (c) Δl/l
     • (d) (Δl/l)³
     उत्तर देखें

     उत्तर: (c)

125. 125. The population inversion between energy states in a Ruby laser is achieved through

     • (a) raising of temperature
     • (b) lowering of temperature
     • (c) optical pumping
     • (d) vacuum pumping
     उत्तर देखें

     उत्तर: (c)