BPSC CCE Prelims
Physics Previous Year Questions (PYQs)
Showing solved Previous Year Questions for Chapter: Physics
Topic Breakdown: Scroll →
A fan produces a feeling of comfort during the hot weather because
Detailed Explanation:
A fan creates air movement that accelerates the evaporation of perspiration from our skin. This evaporation is an endothermic process that absorbs heat from the body, producing a cooling sensation.
The fan does not supply cool air (it merely circulates room-temperature air), nor does it significantly alter body heat radiation or air conductivity—it purely enhances evaporative cooling.
Therefore, perspiration evaporates rapidly, making Option 4 the correct answer.
Twinkling of stars in clear sky during nighttime can be explained with
Detailed Explanation:
Stellar twinkling (or scintillation) occurs because starlight passes through Earth's atmosphere with continuously varying refractive index due to turbulent air layers of different temperatures and densities. This causes the light path to bend unpredictably, making stars appear to twinkle.
Reflection involves bouncing back of light, polarization relates to light wave orientation, and interference involves superposition of waves—none explain atmospheric twinkling.
Therefore, refraction of light is the correct physical phenomenon, making Option 1 the correct answer.
Food gets cooked faster in a pressure cooker because
Detailed Explanation:
In a pressure cooker, the sealed environment increases internal pressure, which raises the boiling point of water above the normal 100°C (at atmospheric pressure). Water boils at a higher temperature (~120°C), transferring more heat energy to food, cooking it faster.
Options 1 and 3 incorrectly state boiling occurs at low temperature, while option 4 wrongly claims low pressure inside the cooker.
Therefore, water boils at high temperature due to high pressure, making Option 2 the correct answer.
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If the doors of a refrigerator are left open for few hours, then the room temperature will
Detailed Explanation:
A refrigerator operates on the Second Law of Thermodynamics: it removes heat from inside and releases it (plus compressor work energy) outside. With doors open, heat expelled into the room exceeds heat absorbed from the room, causing a net temperature increase.
The compressor converts electrical energy into heat, adding extra thermal energy to the room. The cooling effect is localized and temporary, while the heating effect is continuous and distributed.
Therefore, the room temperature will increase, making Option 2 the correct answer.
A piece of ice is floating in a beaker containing water up to its brim. When whole of the ice melts
Detailed Explanation:
When ice floats in water, it displaces a volume of water equal to its own weight. By Archimedes' principle, the mass of displaced water equals the mass of the ice.
When the ice melts, it converts into water of exactly the same mass and occupies the same volume as the water it originally displaced. Therefore, the water level remains unchanged.
Therefore, the water level will not change, making Option 4 the correct answer.
Which of the following is not correctly matched?
Detailed Explanation:
Galvanometer measures small electric currents and detects current direction using needle deflection; it does not measure electric resistance.
Voltmeter measures potential difference, Ammeter measures electric current, and Potentiometer measures electromotive force—all correctly matched.
Therefore, Galvanometer-Electric resistance is incorrectly matched, making Option 4 the correct answer.
If a feather, a rubber ball and a wooden ball are falling freely simultaneously from the same height in vacuum, then
Detailed Explanation:
In a vacuum, all objects fall with the same acceleration (g = 9.8 m/s²) regardless of mass or composition, as demonstrated by Galileo's principle. Without air resistance, a feather, rubber ball, and wooden ball experience identical downward acceleration.
Air resistance normally causes lighter objects like feathers to fall slower on Earth, but in vacuum conditions this factor is completely eliminated, making mass and material properties irrelevant to fall time.
Therefore, all three objects reach the ground simultaneously, making Option 4 the correct answer.
When a soap film on the water is seen in the daytime, it shows beautiful colours. This phenomenon is due to
Detailed Explanation:
Soap film has two surfaces (top and bottom) that reflect light. When white light hits these surfaces, waves reflected from the top and bottom surfaces overlap and interfere, causing certain wavelengths to cancel out and others to amplify, producing the vibrant colours observed.
Diffraction occurs when light bends around edges, refraction is bending due to medium change, and polarization restricts light vibrations to one plane—none explain the colour pattern in soap films.
Therefore, interference of light is responsible for soap film colours, making Option 4 the correct answer.