Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
21. What is the force that is required to produce unit elongation in a wire known as?
[A] Bulk modulus
[B] Thermal strain
[C] Thermal stress
[D] Force constant
Show Answer
Correct Answer: D [Force constant]
Notes:
Force constant of material of wire is the force required to produce unit elongation in a wire. It is denoted by k. K = F/l or K = YA/l
22. What is the shape of meniscus when angle of contact is greater than 90°?
[A] Concave
[B] Convex
[C] Plane
[D] None of the above
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Correct Answer: B [Convex]
Notes:
When angle of contact is greater than 90°, the shape of meniscus is convex. When angle of contact is less than 90°, the shape of meniscus is concave. When angle of contact is equal to 90°, the shape of meniscus is plain.
23. What is the relationship between excess pressure and the radius of the bubble?
[A] are equal in value
[B] inversely proportional to each other
[C] directly proportional to each other
[D] no relationship
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Correct Answer: B [inversely proportional to each other]
Notes:
Excess pressure is inversely proportional to the radius of bubble (or drop). It means that the pressure inside a smaller bubble is higher than inside a larger bubble.
24. Which of the following instruments is used to measure the relative density of a liquid?
[A] Hydrometer
[B] Hygrometer
[C] Lactometer
[D] Gravitimeter
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Correct Answer: A [ Hydrometer ]
Notes:
A hydrometer is an instrument used to measure the specific gravity or relative density of liquids, i.e. the ratio of the density of the liquid to the density of water.
25. What happens to the time period of a spring pendulum based clock kept on the earth when it is taken to moon?
[A] Time period reduces to half
[B] Time period becomes twice
[C] Time period becomes one-sixth
[D] No change
Show Answer
Correct Answer: D [No change]
Notes:
Time of a spring pendulum is independent of acceleration due to gravity. That is why a clock based on spring pendulum will keep proper time every where on a hill or moon or in a satellite and time period of a spring pendulum will not change inside a liquid if damping effects are neglected.
26. What will be the spring constant of each part if the spring of force constant k is divided in to n equal parts?
[A] k
[B] k/n
[C] nk
[D] kn
Show Answer
Correct Answer: C [nk]
Notes:
If the spring of force constant k is divided in to n equal parts then spring constant of each part will become nk.
27. What do we call the distance between two consecutive compressions of a sound wave?
[A] Wave number
[B] Frequency
[C] Wavelength
[D] Amplitude
Show Answer
Correct Answer: C [Wavelength]
Notes:
The distance between two consecutive compressions (C) or two consecutive rarefactions (R) is called the wavelength.
28. What is the measure of the response of the ear to the sound known as?
[A] Pitch
[B] Intensity
[C] Loudness
[D] Amplitude
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Correct Answer: C [Loudness]
Notes:
Loudness is a measure of the response of the ear to the sound. Even when two sounds are of equal intensity, we may hear one as louder than the other simply because our ear detects it better.
29. Which of the following represents the Boiling process?
[A] Adiabatic change
[B] Isothermal change
[C] Isochoric process
[D] None
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Correct Answer: B [Isothermal change]
Notes:
Boiling and Melting both are an example of Isothermal processes because temperature is constant.
30. What is the SI unit of magnetic flux?
[A] teslas
[B] maxwell
[C] weber
[D] Newton
Show Answer
Correct Answer: C [weber]
Notes:
The SI unit of magnetic flux is the weber (Wb) and the CGS unit is the maxwell.
