PES University B. Tech Entrance Exam Physics Model Practice Test with 60 questions and answers.
Ques: Half life of Bi210 is 5 days. If we start with 50,000 atoms of this isft over after days is
(a) 5,000
(b) 25,000
(c) 12,500
(d) 20,000
Ans. (c)
Ques. Line spectra are due to
(a) Hot solids
(b) Atoms in gaseous state
(c) Molecules in gaseous state
(d) Liquid at low temperature
Ans. (b)
Ques. A P-type semiconductor can be obtained by adding
(a) Arsenic to pure silicon
(b) Gallium to pure silicon
(c) Antimony to pure germanium
(d) Phosphorous to pure germanium
Ans. (b)
Ques. The speed of longitudinal wave in a wire is 100 times the speed of transverse waves. If Young’s modulus of the material of the wire is 1.0 x 1011 N/m2, then the stress in wire is
(a) 1.0 x 107 N/m2
(b) 1.5 x 107 N/m2
(c) 1.0 x 1011 N/m2
(d) 1.5 x 1011 N/m2
Ans. (a)
Ques. A spherical mirror forms a real of a point object placed in front. The distance of the image and object from the mirror is 30 cm and 0.2 m respectively. The focal length and nature of the mirror are
(a) 120 mm; concave
(b) 120 mm; convex
(c) 60 cm; concave
(d) 60 cm; convex
Ans. (a)
Ques. The image formed by a convex mirror of focal length 30 cm is a quarter of the size of the object. The distance of the object from the mirror is
(a) 30 cm
(b) 90 cm
(c) 120 cm
(d) 60 cm
Ans. (b)
Ques. That gas cannot be liquified
(a) Which obeys Vander Wall’s equation
(b) Which obeys gas equation at every temperature and pressure
(c) The molecule of which are having potential energy
(d) Which is a inert gas
Ans. (b)
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Ques. A plano-convex lens when silvered in the plane side behaves like a concave mirror of focal length 30 cm. However, when silvered on the convex side it behaves like a concave mirror of focal length 10 cm. Then the refractive index of its material will be
(a) 3.0
(b) 2.0
(c) 2.5
(d) 1.5
Ans. (d)
Ques. “In a forward biased P-N diode, the injected hole current in N-region is proportional to the total charge Q of the injected minority carrier holes” This statement is
(a) True
(b) False
(c) True at law voltage and false at high voltage
(d) True at high voltage and false at low voltage
Ans. (a)
Ques. Two convex lenses of focal lengths 0.3 m and 0.05 m are used to make a telescope. The distance kept between the two is
(a) 0.35 m
(b) 0.25 m
(c) 0.175 m
(d) 0.15 m
Ans. (a)
Ques. The current gain of a transistor in common emitter configuration is 70. If the emitter current is 8.8 mA then the collector current will be
(a) 8.8 mA
(b) 8.68 mA
(c) 0.124 mA
(d) None of these
Ans. (b)
Ques. An astronomical telescope has a length of 1.1 m and a magnifying power ‘10’. The focal lengths of objective and eye lenses are
(a) 0.1 m and 1.0 m
(b) 1.0 m and 0.1 m
(c) 0.6 m and 0.5 m
(d) 0.5 m and 0.5 m
Ans. (b)
Ques. On removing the load from an A.C. circuit if sparks are generated, then the circuit contains
(a) High capacitance
(b) High inductance
(c) High resistance
(d) High impedance
Ans. (b)
Ques. A pure semiconductor behaves slightly as a conductor at
(a) Room temperature
(b) Low temperature
(c) High temperature
(d) Both (b) and (c)
Ans. (a)
Ques. Photo cell is a device to
(a) Store photons
(b) Measure light intensity
(c) Convert photon energy into mechanical energy
(d) Store electrical energy for replacing storage batteries
Ans. (c)
Ques. Which of the following statements is wrong
(a) The centre of the geometrical shadow of a circular opaque disc is always bright
(b) As the size of the disc decreases, the intensity at the centre increases
(c) The intensity in the geometrical shadow of a circular aperture decreases to zero at a very fast rate
(d) The centre of the geometrical shadow of circular aperture is always bright
Ans. (d)
Ques. When current is passed through two straight parallel wires in the same direction, then they
(a) Repel each other
(b) Attract each other
(c) Do not exert any force on each other
(d) Exert some force on each other
Ans. (b)
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Ques. For four wire of same material and same length whose diameters are in the ratio 4 : 3 : 2 : 1, are tied in such a way that each wire gives a node of frequency 3/2 times that of previous one. If the tension in the first wire is 2.048 kg. wt then the tension in the second wire in kg. wt. will be
(a) 2.048
(b) 2.304
(c) 2.462
(d) 2.592
Ans. (d)
Ques. A charged plate has charge density of 2 x 10–6 C/m2 The initial distance of an alactron which is moving towards plate, cannot strike the plate, if it is having energy of 100 eV
(a) 1.77 mm
(b) 3.51 mm
(c) 1.77 cm
(d) 3.51 cm
Ans. (a)
Ques. Two wire of equal diameter, one of iron and another of aluminium wire are sretched by equal tensions. In which wire the velocity of sound will be more
(a) in aluminium wire
(b) in iron wire
(c) in both
(d) not in both
Ans. (a)
Ques. To heat one kg water a heating coil of 2 ohm is connected to a battery of emf 6V and internal resistance 1 ohm. The increase in temperature of water in 7 minutes will be
(a) 0.4°C
(b) 0.8°C
(c) 1.2°C
(d) 1.6°C
Ans. (b)
Ques. Two stars A and B emit maximum radiant energy at wavelengths 4000 Å and 5000 Å respectively. The ratio of their temperatures will be
(a) 2 : 1
(b) 1 : 2
(c) 5 : 4
(d) 4 : 5
Ans. (c)
Ques. The ammeter reading in the adjoining diagram will be
(a) 0.6A
(b) 0.4A
(c) 1.2A
(d) 1A
Ans. (d)
Ques. A cup of tea cools from 80°C to 60°C in one minute. The ambient temperature is 30°C. In cooling from 60°C to 50°C it will take
(a) 90 seconds
(b) 60 seconds
(c) 50 seconds
(d) 30 seconds
Ans. (a)
Ques. Two wires are of same material having lengths in ratio 1 : 2 and diameters in the ratio 2 : 1 For the same force the changes in lengths are in the ratio
(a) 1 ; 4
(b) 4 : 1
(c) 1 : 8
(d) 8 : 1
Ans. (c)
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Ques. The plate resistance and amplification factor of a triode are 10K ohm and 20 respectively. The value of its mutual conductance will be
(a) 2 milli mho
(b) 2 mho
(c) 0.5 mho
(d) 0.5 k mho
Ans. (a)
Ques. Which of following cannot be polarised?
(a) Radio waves
(b) Ultraviolet rays
(c) Infrared rays
(d) Ultrasonic waves
Ans. (d)
Ques. The electron emitted in beat radiation originates from :
(a) inner orbits of atom
(b) free lectrons existing in nuclei
(c) decay of a neutron in a nucleus
(d) photon escaping from the nucleus
Ans. (c)
Ques. Silicon is a semiconductor. If a small amount of As is added to it, then its electrical conductivity
(a) Decrease
(b) Increases
(c) Remains unchanged
(d) Becomes zero
Ans. (b)
Ques. Electromagnetic waves are transverse in nature is evident by
(a) Polarization
(b) Interference
(c) Reflection
(d) Diffraction
Ans. (a)
Ques. A radioactive element has undecayed (1/64) part in 15 hours. Its half life in hours will be
(a) 2.5
(b) 3.5
(c) 7.5
(d) 15
Ans. (a)
Ques. The finite width of spectral lines can be explained on the basis of
(a) Sommerfield theory
(b) Heiseuberg’s uncertainty principle
(c) Schroedinger’s wave theory
(d) De Broglie’s wave theory
Ans. (b)
Ques. 75 cm long sonometer wire is in unision with a fork. If the length of the wire is reduced. By 0.5cm then it produces 3 beats/sec with the fork. The frequency of the fork is
(a) 47.7 Hz
(b) 47.7 Hz
(c) 4.47 Hz
(d) 0.47 Hz
Ans. (b)
Ques. If the energy of a photon corresponding to a wavelength of 6000 Å is 3.32 x 10–19 joule, the photon energy (in joule) for a wavelength of 4000 Å will be
(a) 1.11 x 10–19
(b) 2.22 x 10–19
(c) 4.44 x 10–19
(d) 4.98 x 10–19
Ans. (d)
Ques. The radius of a soap bubble is 2 cm and charge on it is 1.6 x 10–8 C. If the surface tension of soap solution is 0.048 N/m then the excess pressure inside the bubble will be approximately.
(a) 1.9 Pascal
(b) 0.9 Pascal
(c) 9 x 10–3 Pascal
(d) 9.027 Pascal
Ans. (d)
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Ques. A cylinder of mass M and radius R starts falling under gravity at t = 0 as shown in the figure. If the mass of the cord is negligible, the tension in each string will be
(a) Mg/6
(b) Mg/4
(c) Mg/2
(d) Mg
Ans. (a)
Ques. A piece of wire is divided in four equal parts. These are put together to form a bundle. The resistance of the bundle as compared to that of original wire will be
(a) 1/8
(b) 1/6
(c) ¼
(d) 1/16
Ans. (d)
Ques. The atomic mass number of zinc is 66 and its valency is 2. The mass of zinc liberated by 9.65 A of current in 10 seconds will be
(a) 330g
(b) 33 mg
(c) 33 g
(d) 33 kg
Ans. (b)
Ques. The least distance of distinct vision is 25 cm. If the focal length of a convex lens is 10 cm, it acts as simple microscope of maximum magnification
(a) 2.5
(b) 3
(c) 3.5
(d) 5
Ans. (c)
Ques. Water is flowing with a velocity of 2m/s in a horizontal pipe with cross-sectional area decreasing from 2 x 10–2 m2 to 0.01 m2 at pressure 4 x 104 pascal. The pressure at smaller cross-sectional n pascal will be
(a) 32
(b) 3.4
(c) 3.4 x 104
(d) 3.4 x 105
Ans. (c)
Ques. The momentum of a photon of energy hv will be
(a) hv
(b) hv/c
(c) hvc
(d) h/v
Ans. (b)
Ques. Writing on black board with a piece of chalk is possible by the property of
(a) Cohesive force
(b) Adhesive force
(c) Surface tension
(d) Viscosity
Ans. (b)
Ques. Absorption of X-ray is maximum in which of the following different sheets
(a) Copper
(b) Gold
(c) Beryllium
(d) Lead
Ans. (d)
Ques. What will be the power output of 92U235 atomic reactor if it consumes 2Kg fuel in 30 days and the workable energy obtained per fission is 185MeV
(a) 58KW
(b) 58 MW
(c) 58 W
(d) 0 W
Ans. (b)
Ques. Which of the following shows green house effect?
(a) Ultraviolet rays
(b) Infrared rays
(c) X-rays
(d) None of these
Ans. (b)
Ques. When light travels from one medium to the other of which the refractive index is different, then which of the following will change
(a) Frequency, wavelength and velocity
(b) Frequency and wavelength
(c) Frequency and velocity
(d) Wavelength and velocity
Ans. (d)
Ques. Stars are twinkling due to
(a) Diffraction
(b) Reflection
(c) Refraction
(d) Scattering
Ans. (c)
Ques. When a source of sound crosses an observer then change in apparent frequency observed by the observer is 2% its initial frequency. If the speed of sound is 350m/s then the velocity of source will be
(a) 3.5m/s
(b) 3.5 cm/s
(c) 3.5 ft./s
(d) Zero
Ans. (a)
Ques. A hot liquid takes 5 minutes to cool from 70°C to 60°C. The time taken by the same liquid to cool from 60°C to 50°C will be
(a) 1s
(b) 2s
(c) 3s
(d) 4s
Ans. (c)
Ques. The dimensions of thermal resistance are
(a) M–1L–2T3K
(b) ML2T–2K–1
(c) ML2T–3K
(d) ML2T–2K–2
Ans. (a)
Ques. A double convex lens is made of glass of refractive index 1.5. If its focal length is 30 cm, then radius of curvature of each of its curved surface is
(a) 10 cm
(b) 15 cm
(c) 18 cm
(d) None of these
Ans. (d)
Ques. The energy received from sun on earth is 8.4 J/minute cm2. The solar energy incident on an area of 10m2 is given to 100 gm of water in a bowl at 0°C. The water will start boiling after
(a) 5 minute
(b) Greater than 5 minutes
(c) Less then 5 minutes
(d) Some times greater and some times less than 5 min
Ans. (b)
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Ques. An observer is standing at the bank of sea and finds that 54 waves are reaching the bank per minute. If the wave length of waves is 10 meter then their speed will be
(a) 3 m/s
(b) 9 m/s
(c) 332 m/s
(d) zero
Ans. (b)
Ques. The mean distance of sun from the earth is 1.5 x 108 Km (nearly). The time taken by the light to reach earth from the sun is
(a) 0.12 min
(b) 8.33 min
(c) 12.5 min
(d) 6.25 min
Ans. (b)
Ques. The steel railway track is to be stopped from expanding at the joints due to temperature increase. If the area of cross-section of the track is 100 cm2 then the elastic potential energy stored per meter in the track due to temperature increase of 10°C will be
(a) 288 Joule
(b) 144 Joule
(c) 28.2 Joule
(d) 14.4 Joule
Ans. (d)
Ques. A convex lens of power + 6D is placed in contact with a concave lens of power – 4D. What is the nature and focal length of the combination
(a) Concave, 25 cm
(b) Convex, 50 cm
(c) Concave, 20 cm
(d) Convex, 100 cm
Ans. (b)
Ques. Resistivity of a semiconductor depends on
(a) Shape of semiconductor
(b) Atomic nature of semiconductor
(c) Length of semiconductor
(d) Shape and atomic nature of semiconductor
Ans. (b)
Ques. Boolean algebra is essentially based on
(a) Truth
(b) Logic
(c) Symbol
(d) Numbers
Ans. (b)
Ques. If the forward voltage in a diode is increased, the width of the depletion region:
(a) increases
(b) decreases
(c) fluctuates
(d) no change
Ans. (b)
Ques. A ball is released from the top of a tower. The ratio of work done by force of gravity in first, second and third second of the motion of the ball is
(a) 1 : 2 : 3
(b) 1 : 4 : 9
(c) 1 : 3 : 5
(d) 1 : 5 : 3
Ans. (c)
Ques. The heat of neutralization of HCl by NaOH under certain condition is – 55.9 kJ and that of HCN by NaOH is –12.1 kJ. the heat of ionization of HCN is
(a) –68.0 kJ mol–1
(b) –43.8 kJmol–1
(c) 68.0 kJmol–1
(d) 43.8 kJmol–1
Ans. (d)
