BPSC TRE Previous Question Paper Quiz
विद्यालय अध्यापक परीक्षा के पूछे गए प्रश्न
For Class (1-5), (6-8), (9-10), (11-12)
Results
#1. During an experiment, quantities a, b, c are measured and parameter Y = ab²/c⁴ is calculated. If the maximum percentage errors in the measurement of a, b and c are respectively 1%, 2% and 3%, then the maximum percentage error in Y would be
Explanation: Error = 1 + (2×2) + (4×3) = 17%. Powers multiply percentage error contribution.
#2. What is an oscillator’s proportionality constant if the damping force is proportional to the velocity?
Explanation: From F = bv, unit of b is (N·s/m) = kg/s.
#3. A particle is projected with speed u from the top of a plane inclined at an angle θ with the horizontal. The distance from the point of projection to where the particle strikes the plane will be
Explanation: Range on an inclined plane for projectile motion simplifies to (2u²/g) tanθ secθ.
#4. The specific heat of a substance can be
Explanation: In special thermodynamic systems such as stars, specific heat may be zero or negative.
#5. A block of mass 2 kg is pulled up on a smooth incline of angle 30° with the horizontal. If the block moves with an acceleration of 2 m/s², then the average power delivered 4 seconds after the motion starts, will be
Explanation: Force = m(a + g sin30°) = 13.8 N and v = 8 m/s → Power = Fv = 110.4 W.
#6. The ratio of average velocity and average speed of a body is
Explanation: Velocity depends on displacement while speed depends on total path, so the ratio ≤ 1.
#7. In a head-on elastic collision of two bodies of equal mass
Explanation: In equal-mass elastic collision, velocities exchange, causing momentum swap and speed reversal.
#8. Which of the following energy changes involves frictional forces?
Explanation: Friction converts mechanical energy directly into thermal energy.
#9. A body falling freely from a height H hits an inclined plane in its path at a height h. Due to impact, the direction of velocity of the body becomes horizontal. For the body to take maximum time to reach the ground, h/H should be in the ratio
Explanation: Time function is maximized when h = H/2, giving h/H = 1/2.
#10. When you stretch a rubber band, the energy transferred is stored in the form of
Explanation: Stored energy is elastic potential energy within the rubber.
#11. A piece of wood of mass 0.03 kg is dropped from the top of a building 100 m high. At the same time, a bullet of mass 0.02 kg is fired vertically upward with a velocity of 100 m/s from the ground. The bullet gets embedded in the wooden piece after striking it. The time of strike would be
Explanation: Equating displacements gives 100 = 100t → t = 1 s.
#12. A machine gun fires 60 bullets per minute with a velocity of 700 m/s. If each bullet has a mass of 50 g, then the power developed by the machine gun is
Explanation: One bullet per second → KE = ½mv² = 12250 J → power = 12250 W.
#13. A block of mass m is pushed against a spring with spring constant k fixed at one end to a wall. The block slides on a frictionless table resting against this wall. The natural length of the spring is L and is compressed to half its natural length when the block is released. The velocity of the block after the spring acquires its natural length would be
Explanation: Energy stored = ½k(L/2)²; converting to kinetic gives v = (L/2)√(k/m).
#14. How much work is done in moving a charge of 5 C across two points having a potential difference of 16 V?
Explanation: W = qV = 5 × 16 = 80 J.
#15. Suppose you lift a suitcase lying on the floor and place it on a table. The work done by you on the suitcase does not depend on
Explanation: Work depends only on weight and height, not time or path.
#16. The angular momentum of a rigid body is L. If its kinetic energy is halved, what will be its angular momentum?
Explanation: L ∝ √K so L becomes L/√2, which is not listed.
#17. Consider a light rod with two heavy mass particles mA and mB attached to its ends. Let XY be a line perpendicular to the rod at a distance r₁ from mass mA and r₂ from mass mB. The moment of inertia of the system about XY would be
Explanation: For point masses, I = Σmr².
#18. When does the moment of inertia of a body come into the picture?
Explanation: It measures resistance to rotational acceleration
#19. Two unequal masses are tied together with a compressed spring. When the chord is burnt with a matchstick releasing the spring, the two masses will fly apart with equal
Explanation: Internal forces conserve linear momentum.
#20. Thermal expansion in solids with increasing temperature is the consequence of
Explanation: Non-linear bonding increases equilibrium spacing with temperature.
#21. A steel wire of 0.8 mm diameter and length 1 m is clamped firmly at points A and B, which are 1 m apart and in same plane. A body of mass M is hung at the middle of the wire such that midpoint sags by 1 cm from the original position. If Y = 2 × 10¹¹ N/m² for the wire, then the mass of the body would be
Explanation: Using strain and stress relation with small sag approximation gives M ≈ 0.082 kg. Wire geometry and elasticity determine force.
#22. Inert gases exhibit
Explanation: Inert gases have paired electrons, so they show weak diamagnetism. They don’t have unpaired spins for paramagnetism
#23. In the absence of external forces, the shape of a small liquid drop is determined by
Explanation: Surface tension minimizes surface area, forming a spherical drop. Other properties do not define shape directly.
#24. What is the energy required to move a body of mass m from an orbit with radius 2R to another orbit of radius 3R?
Explanation: Change in gravitational potential energy between two circular orbits gives ΔU = GMm(1/2R − 1/3R). Simplifying gives GMm / 6R.
#25. In streamline flow
Explanation: In streamline flow, particles follow same path and conditions at that point, leading to equal kinetic energy.
#26. If the temperature increases, what happens to the modulus of elasticity?
Explanation: Increased temperature weakens intermolecular bonding, reducing stiffness, and hence elasticity.
#27. When 1 kg of ice melts at 0°C into water at the same temperature, the change in entropy is
Explanation: ΔS = L/T = 80 cal / 273 K ≈ 0.293 cal/K. Since temperature is constant, formula applies directly.
#28. A force is exerted at 30° angle to a cube that is fixed on a table surface. What kind of transformation will the cube go through?
Explanation: The applied force has both shear and compressive components, causing deformation in dimensions and shape.
#29. One mole of a perfect gas expands adiabatically which changes its pressure P₁, volume V₁ and temperature T₁ to P₂, V₂ and T₂ respectively. If the molar specific heat at constant volume is Cᵥ, then the work done by the gas would be
Explanation: For adiabatic process work done equals decrease in internal energy: W = Cᵥ (T₁ − T₂). Heat exchange is zero
#30. Which of the following materials is unaffected by an applied elastic force?
Explanation: Quartz exhibits negligible strain and shows extremely high elastic modulus, so deformation under normal stress is insignificant.
#31. The motion of Halley Comet around the Sun is not
Explanation: Orbit is elliptical periodic motion, but not SHM because restoring force and path do not satisfy SHM conditions.
#32. The amount of energy required to raise the temperature of a substance of 1 kg mass by 1°C is called
Explanation: Specific heat capacity defines temperature change per unit mass per degree increase.
#33. On a certain day, the temperature and relative humidity of air are respectively 20°C and 80%. If the saturation vapour pressures at 20°C and 5°C are respectively 17.5 mm of Hg and 6.5 mm of Hg, then the fraction of mass of water that condenses on falling of temperature to 5°C will be
Explanation: Initial vapour = 0.8 × 17.5 = 14 mm; final capacity = 6.5 mm; condensing fraction = (14 − 6.5)/14 ≈ 0.48.
#34. In an isobaric expansion of a gas
Explanation: At constant pressure (ideal gas law), V ∝ T, so both increase together.
#35. Consider a mixture of oxygen and hydrogen kept at room temperature. In comparison to H₂ molecule, O₂ molecule hits the wall of container with
Explanation: Speed ∝ 1/√m; since O₂ is heavier, it travels slower at the same temperature.
#36. In thermodynamics, which of the following statements are true? (1) Work is a path-independent function. (2) Work is a path-dependent function. (3) Work is the area under the curve in a P–V diagram. (4) Work and heat energy are completely interchangeable.
Explanation: Work depends on process path and equals ∫PdV (area under P-V curve)
#37. When the temperature of a gas in a rigid container is raised, the pressure exerted by the gas on the container wall increases because
Explanation: Higher temperature means higher kinetic energy, causing stronger and more frequent collisions.
#38. Which of the following techniques cannot be used for generating electron-hole pairs in electronic devices?
Explanation: Doping introduces carriers but does not generate electron-hole pairs through excitation
#39. Two periodic waves of amplitudes A₁ and A₂ such that A₁ > A₂ pass through a region. The difference between maximum and minimum resultant amplitudes possible is
Explanation: Minimum resultant amplitude = A₁ − A₂; maximum change in amplitude = 2A₂.
#40. If the temperature of the source is increased, the efficiency of Carnot engine
Explanation: η = 1 − Tc/Th; increasing Th increases efficiency.
#41. Three charges +4q, Q and q are placed in a straight line of length l at points distant 0, l/2 and l respectively. The value of charge Q, in order to make the net force on q zero, would be
Explanation: Force balance gives Q = −2q at midpoint for equal and opposite electric forces.
#42. According to the law of equipartition of energy, the molar specific heat of solids depends on
Explanation: Classical theory predicts constant molar specific heat (3R), independent of mass and temperature.
#43. Kirchhoff’s voltage law is satisfied for
Explanation: KVL holds when passive elements behave linearly and do not store energy non-linearly.
#44. The Vᵣₘₛ of a gas molecule is 300 m/s. If its absolute temperature is reduced to half and molecular weight is doubled, then the Vᵣₘₛ will become
Explanation: Vrms ∝ √(T/M). Halving temperature and doubling mass reduces speed by factor 4 → 300/4 = 75 m/s.
#45. In copper atom, 29 electrons surround its nucleus. Consider two pieces of copper each weighing 10 g. Let us transfer one electron from one piece to another for every 1000 atoms in the piece. The Coulombic force between these two pieces of copper kept 10 cm apart after transfer of electrons will be
Explanation: Charge transfer calculation with Coulomb’s law gives large repulsive force ≈ 2.08 × 10¹⁴ N.
#46. What is the relation between kinetic energy (E) of a gas and its pressure (P)?
Explanation: From kinetic theory of gases: ( PV = \frac{2}{3}E ).
#47. A metallic sphere A of radius a is charged to a potential V. If this sphere is enclosed by a spherical conducting shell B of radius b (b > a) and interconnected through a wire, the potential on sphere A would be
Explanation: With grounded shell, potential scales with ratio of radii → V’ = aV/b.
#48. What is the phase difference between the tuning fork’s prongs?
Explanation: Prongs oscillate in opposite phases, giving a phase difference of 180° = π rad.
#49. An electric iron draws 10 A, an electric toaster draws 5 A and an electric refrigerator draws 3 A from 220 V service line. If all the three appliances, connected in parallel, operate at the same time, the rating of the fuse for their operation should be
Explanation: Total current = 18 A, so fuse should be slightly above—20 A.
#50. When a wave is reflected from a denser medium, how does the phase change?
#51. An electron moving East is acted on by a magnetic field in North direction. The force on the electron is
Explanation: Using Fleming’s rule and negative charge direction, force is downward.
#52. A particle is undergoing an SHM with a 10 cm amplitude. What should be the minimum acceleration at an extreme point for the maximum speed at the centre to be 5 m/s?
Explanation: vmax = ωA → ω = 50 rad/s → amax = ω²A = 250 m/s².
#53. A capacitor is connected to a 12 V battery through a 10 ohm resistance. It is found that the potential difference rises to 4 V in 1 μs. The capacitance value would be
Explanation: Using charging law V = V₀(1 − e⁻ᵗ/RC), solving gives C ≈ 0.25 μF.
#54. A plane progressive wave is given by y = 25 cos(2πt − πx). Then the amplitude and frequency are respectively given as
Explanation: Amplitude = 25 and frequency = coefficient of time/2π = 2π/2π = 1 Hz.
#55. A ferromagnetic material is placed in external magnetic field. The magnetic domains
Explanation: Domains align and grow in direction of applied field.
#56. A 4 kg block is attached to a spring of spring constant 400 N/m. Calculate the time period of oscillations.
Explanation: ( T = 2π\sqrt{m/k} = 2π√(4/400) = π ).
#57. If →E and →B represent electric and magnetic field vectors in an e.m. wave, then the direction of propagation of the wave would be
Explanation: Wave travels perpendicular to both electric and magnetic fields via cross product.
#58. How is the electric field at the surface of a charged conductor related to the surface charge density?
Explanation: ( E = σ/ε₀ ), so directly proportional to surface charge density.
#59. An inductor, a resistor and a capacitor are connected in series with a.c. source. With increase of source frequency slightly from a very low value, the reactance
Explanation: ( X_L ∝ f ) while ( X_C ∝ 1/f ), so initially only the inductor reactance rises.
#60. What is the order of magnitude of the resistance of a dry human body?
Explanation: Typical resistance of dry skin is around 10 kΩ.
#61. Lenz law is the consequence of the conservation of
Explanation: Lenz’s law ensures induced current opposes change, conserving energy. Without this opposition perpetual motion would be possible.
#62. Mobility is denoted by
Explanation: Electron mobility is represented by μ and indicates drift velocity per unit electric field
#63. If E and B are electric and magnetic fields, then which of the following is dimensionless quantity?
Explanation: Since √(μ₀ε₀) = 1/c, multiplying with E/B yields a dimensionless ratio
#64. Which of the following is non-ohmic resistance?
Explanation: Both lamp filament and diode do not follow Ohm’s law due to temperature dependence and non-linear I-V characteristics
#65. When the diameter of the aperture of the objective of an astronomical telescope increases, its
Explanation: Magnification depends on focal lengths; larger aperture improves resolution but not magnification.
#66. The nature of magnetic field lines passing through the centre of a current-carrying circular loop is
Explanation: At the centre field is uniform and directed perpendicular to plane of loop
#67. The conduction current is same as displacement current when the source is
Explanation: Displacement current appears where electric field varies, which happens in AC but not steady DC.
#68. The light energy emitted by a star is due to
Explanation: Stars produce energy through nuclear fusion, where lighter nuclei join to form heavier ones.
#69. In a diffraction pattern, the fringe width is
Explanation: Narrower slit increases diffraction, widening the fringes ((β ∝ 1/a)).
#70. What happens to the quality factor of an L-C-R circuit if the resistance is increased?
Explanation: (Q = 1/R \sqrt{L/C}), so increasing resistance lowers Q-factor.
#71. The de Broglie wavelength associated with neutrons in thermal equilibrium with matter at 300 K is
Explanation: Using thermal energy approximation formula, neutrons at room temperature have wavelength ≈ 18 Å.
#72. When is the current in a circuit wattless?
Explanation: Without resistance, power consumed is zero even though current flows (purely reactive circuit).
#73. Photoelectric emission can be explained by the
Explanation: It requires both particle explanation (photons) and quantization principles
#74. Which microwave component uses the principle of Faraday Rotation?
Explanation: Microwave isolators use Faraday rotation to allow transmission in one direction only.
#75. A proton and an electron are accelerated by same potential difference. In this case, de Broglie wavelength of the electron, λₑ and of the proton, λₚ are such that
Explanation: Lighter particles have greater de-Broglie wavelength at same kinetic energy.
#76. Large number of thin strips of black paint are made on the surface of a convex lens of focal length 20 cm to catch the image of a white horse. The image will be
Explanation: Only intensity reduces; image remains same because lens aperture is reduced.
#77. The total energy of electron in the nth orbit of hydrogen atom is
Explanation: Bohr model gives total energy (E = – \frac{1}{2} (e²/4πε₀rₙ)).
#78. The emission of electrons from the surface of metal, when the radiation of appropriate frequency is allowed to incident on it, is called
Explanation: When photons strike a metal surface they can eject electrons if threshold frequency is met.
#79. During a nuclear fission reaction
Explanation: Controlled fission requires a heavy nucleus like U-235 absorbing a slow neutron.
#80. In nuclear reactions, there is a conservation of
Explanation: Nuclear reactions conserve energy, momentum and charge.
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