# Physics – Science – WBCS Main Question Paper

Contents ## WBCS Main Question Paper – 2019

31. Black holes were predicted by
(A) Copernicus
(B) Einstein
(C) Rutherford
(D) Satyen Bose

114. Which of the following electromagnetic waves have the smallest wavelength?
(A) Infrared rays
(B) UV rays
(C) X-rays
(D) y-rays

128. Which of these are used to measure optical activity?
(A) Polarimeter
(B) Planometer
(C) Psychrometer
(D) Photometer

131. The emission spectrum of hydrogen discovered first and the region of the electromagnetic spectrum in which it belongs, respectively are
(A) Lyman, ultraviolet
(B) Lyman, visible
(C) Balmer, ultraviolet
(D) Balmer, visible

136. A bullet on penetrating 30 cm into its target loses it’s velocity by 50%.What additional distance will it penetrate into the target before it comes to rest?
(A) 30 cm
(B) 20 cm
(C) 10 cm
(D) 5 cm

137. In which of the following phenomena, the heat waves travel along straight lines with the speed of light?
(A) Thermal conduction
(B) Forced convection
(C) Natural convection

139. If the band gap between valence band and conduction band in a material is 5.0eV, then the material is
(A) semiconductor
(B) good conductor
(C) super conductor
(D) insulator

142. In which of the following pairs, the two physical quantities have different dimensions?
(A) Planck’s constant and angular momentum
(B) Impulse and linear momentum
(C) Moment of inertia and moment of a force
(D) Energy and torque

143. Water is flowing through a very narrow tube. The velocity of water below which the flow remains a streamline flow is known as
(A) relative velocity
(B) terminal velocity
(C) critical velocity
(D) particle velocity
144. An electric bulb marked as 50 W-200 V is connected across a 100 V supply. The present power of the bulb is
(A) 37.5 W
(B) 25 W
(C) 12.5 W
(D) 10 W

151. A body is floating in a liquid at rest. Incorrect statement about situation options:
(A) Buoyancy is equal to weight of body.
(B) Weight of liquid displaced by body is equal to buoyancy.
(C) Force applied by body on liquid is buoyancy downward.
(D) Weight will be greater than buoyancy.

152. The noise level during plane take off is around
(A) 100 dB
(B) 150 dB
(C) 200 dB
(D) 250 dB

172. The potential energy of a molecule on the surface of a liquid compared to one inside the liquid is
(A) zero
(B) lesser
(C) equal
(D) greater

173. For a metallic wire, the ratio v/i  [ v = applied potential difference and i = current flowing ] is
(A) independent of temperature.
(B) increases as the temperature rises.
(C) decreases as the temperature rises.
(D) increases or decreases as the temperature rises depending upon the metal.

193. The value of the compressibility of an ideal fluid is
(A) zero
(B) unity
(C) infinity
(D) more than that of a real fluid

194. In electromagnetic theory, continuity equation relates ______
(A) volume conservation
(B) mass conservation
(C) charge conservation
(D) energy conservation

195. Which is the cheapest device for measuring flow/discharge rate?
(A) Venturimeter
(B) Pitot tube
(C) Orifice Meter
(D) None of the above

## WBCS Main Question Paper – 2018

25. If the current passing through a resistance increase by two times, the heat generated will increase by
a) 2 times
b) 4 times
c) 6 times
d) 8 times

26. Atomic defect responsible for reduction of bulk density of the material :
a) Schottky
b) Frankel
c) Interstitial
d) Electronic

27. Largest amount of energy, the earth receiving from the sun is in the form of
a) Infrared and heat energy
b) Y -rays
c) UV-rays
d) X-rays

31. Electric power has the unit of
a) Volt
b) Watt
c) Coulomb
d) Ampere

35. Which material is used for production of automobile spring requiring high elastic property ?
a) Copper
b) Steel
c) Brass
d) All of the above

36. Sound wave having frequency more than 20,000 Hertz is known as
a) Ultrasonic
b) Supersonic
c) Microwave
d) Seismic

37. Spin of ‘Boson’ particle is equal to
a) positive integer
b) negative integer
c) positive integral multiple of 1/2
d) any fraction

39. Walk on a smooth floor causes fatal fall because
a) grip of legs with the floor surface minimizes
b) frictional force nil
c) centre of gravity of body changes
d) increase of forwarding forces

43. Quality of a musical note depends on
a) fundamental frequency
b) harmonics
c) amplitude of the wave
d) velocity of sound

44. Wavelength of visible light lies in between
a) 400 to 800 mm
b) 500 to 1000 mm
c) 300 to 600 mm
d) 200 to 400 mm

45. The device that converts AC to DC is called
a) Transformer
b) Rectifier
c) Induction motor
d) Dynamo

79. The electrical resistivity of a semiconductor
a) increases with temperature.
b) decreases with temperature
c) does not change with temperature.
d) increases at lower temperature but decreases at higher temperature.

73. A Carnot engine operating between 27°C and 127°C has efficiency:
a) 21%
b) 22%
c) 24%
d) 25%

75. The pressure gauge used for measuring very low vacuum of the order of lO torr:
a) Bourdon pressure gauge
b) Hot filament ionisation gauge
c) McLeod gauge
d) Inclined tube manometer

92. The resistance of an ideal ammeter is
a) zero
b) small
c) high
d) very high

93. Solar spectrum is the example of
a) continuous emission spectrum
b) band absorption spectrum.
c) line absorption spectrum
d) continuous absorption spectrum.

## WBCS Main Question Paper – 2017

51. An internal combustion engine runs on the principle of
(A) Otto cycle
(B) Diesel cycle
(C) Carnot cycle
(D) Ranking cycle

52. Who presented first the experimental value of G ?
(A) Newton
(B) Cavendish
(C) Galileo
(D) None of the above

53. A geostationary satellite has an orbital period of
(A) 2 hours
(B) 6 hours
(C) 12 hours
(D) 24 hours

54. When the milk is churned vigorously, the cream Is separated due to
(A) Fractional force
(B) Centrifugal force
(C) Centripetal force
(D) Gravitational force

55. Weber is the unit of
(A) Intensity of magnetization
(B) Permeability
(C) Magnetic flux
(D) Magnetic susceptibility

56. One nanometer is equal to
(A) 10-15 m
(B) 10-9 m
(C) 10-18 m
(D) 10-12 m

153. Water attains maximum density at
(A) 0°C
(B) 4°F
(C) 4K
(D) 4°C

154. If two bulbs of 25 W and 100 W rated at 220 V, are connected in series across 440 V supply
(A) 25 W bulb will fuse
(B) 100 W bulb will fuse
(C) None of these will fuse
(D) Both will fuse.

156. If the lengths and two diagonals of a rectangle are each increased by 6%, find % increase in its breadth.
(A) 5%
(B) 6%
(C) 7%
(D) 8%

157. The aspect ratio is the ratio of
(A) x axis : y axis
(B) Sinθ : Cosθ
(C) Length : Width
(D) None of the above
158. Refractive index of a medium is defined by
(A) the ratio of the cosine of the angles of incidence and refraction of light is constant when it passes between two given media.
(B) the ratio of the sine of the angles of refraction and incidence of light is constant when it passes between two given media.
(C) the ratio of the sine of the angles of incidence and refraction of light is constant when it passes between two given media.
(D) None of the above

173. The Crown glass is an
(A) Optical glass
(C) Safety glass
(D) Toughened glass

174. An intrinsic semiconductor has forbidden gap of
(A) 2eV
(B) >2eV
(C) <2eV      (0.7 eV)
(D) None of the above

177. The specific gravity of ß-quartz is
(2.65 g/cc; 2.59 – 2.63 in impure varieties)
(A) 2.32 g/cc
(B) 2.63 g/cc
(C) 2.53 g/cc
(D) 2.2 g/cc

195. (Ni-Mn) ferrite is the example of material
(A) ferrimagnetic
(B) paramagnetic
(C) ferromagnetic
(D) None of the above

196. Soft iron is used in many parts of electrical machines for its
(A) Low hysteresis loss and low permeability
(B) High hysteresis loss and low permeability
(C) Large density and large retentively
(D) Low hysteresis loss and high permeability

197. Tangent galvanometer is used to measure
(B) Currents impulses
(C) Earth’s magnetic field
(D) None of the above

198. In a charged capacitor, the energy is stored as
(A) Positive charge
(B) both as positive and negative charge
(C) the electric field between the plates
(D) the potential energy of the capacitor plates

199. Line spectrum is produced by
(A) the Sun
(B) mercury vapour lamp
(C) candle
(D) electric bulb

## WBCS Main Question Paper – 2016

8. The electrical circuits used to get smooth D.C. output from a rectified circuit is called –
(A) amplifier
(B) filter
(C) oscillator
(D) full wave rectifier

11. Which one among the following has the highest energy ?
(A) Blue light
(B) Green light
(C) Red light
(D) Yellow light

12. Cylindrical lens is used by a person suffering from –
(A) astigmatism
(B) myopia
(C) hypermetropia
(D) pres biopia

13. To an observer on the lunar surface, during the day time the sky will appear to be –
(A) light yellow
(B) orange
(C) blue
(D) black

14. What is viewed through an electron microscope ?
(A) Electrons and other elementary particles
(B) Structure of bacteria and viruses
(C) Inside of human stomach
(D) Inside of the human eye

15. When viewed in white light, soap bubbles show colours because of –
(A) scattering
(B) diffraction
(C) interference
(D) dispersion

16. In electric supply lines in India, which parameter is kept constant ?
(A) Voltage
(B) Current
(C) Frequency
(D) Power

17. What is the most commonly used substance in fluorescent tubes ?
(A) Sodium oxide and argon
(B) Sodium vapour and neon
(C) Mercury vapour and argon
(D) Mercury oxide and neon

18. Which one of the following is printed on a commonly used fluorescent tube light ?
(A) 220 K
(B) 275 K
(C)  6500 K
(D) 9000 K

19. Electricians use rubber glaves while working  because –
(A) rubber is a good conductor
(B) rubber is an insulator
(C) it is easy to work while wearing gloves
(D) None of the above
20. Which type / types of pen uses / use capillary action in addition to gravity for flow of ink ?
(A) Fountain pen
(B) Ball point pen
(C) Gel pen
(D) Both ball point and gel pens

21. Parsec is a measure of –
(3.26156 light year)
(A) brightness of heavenly bodies
(B) density of the earth
(C) orbital velocity of the stars
(D) astronomical distance

26. Which of the following Persons discovered the gamma rays ?
(A) Paul Villard
(B) Marie Curie
(C) J. J. Thompson

27. Confirmation of the presence of Higgs Boson will justify –
(A) both the standard model and superstring theory
(B) the unification of all the four fundamental forces
(C) the steady state model of the universe
(D) the mass of the fundamental particles

29. When red glass is heated in dark room it will seem –
(A) green
(B) purple
(C) black
(D) yellow

30. A refrigerator, with its power on, is kept in closed room with its door open. The temperature of the room will –
(A) fall
(B) rise
(C) remain the same
(D) None of these

31. Cooking taken longest time –
(A) at Shimla
(B) at Mt. Everest
(C) at the sea level
(D) None of these

47. In nuclear reaction, there is conservation of-
(A) energy only
(B) momentum only
(C) mass, energy and momentum
(D) mass only

50. The mass-energy relation is the outcome of –
(A) quantum theory
(B) general theory of relativity
(C) field theory of relativity
(D) special theory of relativity

51. Who firstly demonstrated experimentally the existence of electromagnetic waves ?
(A) Hertz      (Germany)
(B) Romar
(C) Marconi
(D) Maxwell
53. Silica in amorphous form is used in –
(A) photovoltaic cell
(B) conductivity cell
(C) standard hydrogen electrode
(D) None of these

57. Fat can be separated from milk in a cream separator because of
(A) cohesive force
(B) gravitational force
(C) centripetal force
(D) centrifugal force

70. If the earth was stop rotating, the value of ‘g’ –
(Equator – increases, Poles – unchanged)
(A) Increases
(B) decreases
(C) remain unchanged
(D) becomes zero

76. The celsius temperature is a / an –
(A) relative temperature
(B) absolute temperature
(C) specific temperature
(D) approximate temperature

77. Weightlessness experienced in spaceship is due to
(A) absence of inertia
(B) absence of accelerating force
(C) absence of gravity
(D) free fall of the spaceship

82. The internal resistance of a dry cell is-
(A) equal to that of electrolytic cell
(B) smaller than that of electrolytic cell
(C) higher than that of electrolytic cell
(D) zero

83. Which of the following is the example of ideal black body ?
(A) Blackboard
(B) Kajol
(C) A pin hole box
(D) None of the above

84. REM is a unit of –
(B) binding energy
(C) packing fraction

95. Entropy change of a system and its surroundings in equilibrium –
(A) increases
(B) decrease
(C) remains constant
(D) either increases or decreases

104. A small and a large rain drops are falling through air –
(A) the small drop moves faster
(B) the large drop moves faster
(C) both moves with same speed
(D) None of the above
105. If a bomb dropped from an airplane explodes in midair –
(A) its KE increases
(B) its total energy increases
(C) its total energy decreases
(D) None of these

67. Which of the following is a closed system ?
(A) Jet engine
(B) Tea placed in steel kettle
(C) Pressure cooker
(D) Rocket engine during propulsion

107. Nights are cooler in the deserts than in the plain because
(A) sand radiate heat more quickly than the earth
(B) the sky remains clear most of the time
(C) sand absorbs heat quickly than the earth
(D) None of the above

114. Which of the following is used by the mountaineers and the pilots to measure pressure ?
(A) Simple barometer
(B) Fortin’s barometer
(C) Manometer
(D) Aneroid barometer

124. Red shifts is an illustration of –
(A) high frequency absorption
(B) low temperature emission
(C) doppler effect
(D) unknown phenomenon

125. What is the principle by which a cooling system (radiator) in a motor car works ?
(A) Convection
(B) Conduction only

## WBCS Main Question Paper – 2015

1. Diffusion of light in atmosphere takes place due to
(A) Dust Particles
(B) Carbon dioxide
(C) Helium
(D) Water Vapour

2. A weightless rubber balloon is filled with 200c.c. of water. Its weight in water is equal to
(A) 9.8/5 N
(B) 9.8/10 N
(C) 9.8/2 N
(D) Zero

3. A car is running on a road at a uniform speed of 60 km/h. The net resultant force on the car is
(A) Driving force in the direction of motion of the car
(B) Resistance force in the direction opposite to car’s motion
(C) An inclined force
(D) Equal to Zero

7. Rainbow is produced when sunlight falls on drop of rain. The physical phenomena responsible for this are
1) Dispersion
2) Refraction
3) Internal reflection
(A) 1 & 2
(B) 2 & 3
(C) 1 & 3
(D) All of the above

44. David Bushnell is credited with the creating of
(A) First submarine    (1775)
(B) Hovercraft
(C) Steamship
(D) Catamaron

45. Which one of the following is printed on a commonly used fluorescent tube light?
(A) 220 K
(B) 273 K
(C) 6500 K
(D) 9000 k

5. Who among the following scientists shared the Nobel Prize in Physics with Son
(A) Max Planck
(B) Albert Einstein
(C) William Henry Bragg    (1915)
(D) Enrico Fermi

43. Sir C.V. Raman was awarded Nobel prize in the year
(Physics – Raman effect)
(A) 1920
(B) 1925
(C) 1930
(D) 1931

92. A sample of gas expands from volume V1  to V2. The amount of work done by gas is greatest when the expansion is
(B) Equal in all cases
(C) Isothermal
(D) Isobaric

93. Blue colour of the sky is due to the phenomenon of
(A) Scattering
(B) Dispersion
(C) Reflection
(D) Refraction
94. Electron Volt is the unit of
(A) Potential difference
(B) Charge
(C) Energy
(D) Power

96. Photoelectric emission occurs only when the incident light has more than a certain minimum
(A) Power
(B) Wavelength
(C) Intensity
(D) Frequency

97. Fluorescent tubes are fitted with a choke. the choke coil
(A) Steps up the line voltage
(B) Steps down the line voltage
(C) Reduces the current in the circuit
(D) Chekes low frequency current

98. A ‘black hole’ is a body in space which does not allow any radiation to come out. This property is due to its
(A) Very small size
(B) Very large size
(C) Very high density
(B) Very Very low size

100. If the radius of the Earth were to shrink by one percent its mass remaining the same the value of ‘g’ on the earth’s surface would
(A) Increase by 0.5%
(B) Increase by 2.0%
(C) Decrease by 0.5%
(D) Decrease by 2.0%

184. Several colours on the screen of colour television are produced by mixing lights of colours
(A) red, yellow green
(B) Red, yellow, Blue
(C) Red, Green, Blue
(D) Yellow, Green, Blue

## WBCS Main Question Paper – 2014

1.  Newton’s third law gives directly the law of conservation of
(A) Momentum
(B) Energy
(C) Angular Momentum
(D) Power

11.  The wave length of visible light lies between 