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. Who invented mercury barometer?
[A] Blaise Pascal
[B] Daniel Bernoulli
[C] Albert Einstein
[D] Evangelista Torricelli
Show Answer
Correct Answer: D [Evangelista Torricelli]
Notes:
Evangelista Torricelli devised for the first time a method for measuring atmospheric pressure. A long glass tube closed at one end and filled with mercury is inverted into a trough of mercury. This device is known as ‘mercury barometer’.
22. What is the SI unit of viscosity?
[A] candela
[B] poiseiulle
[C] Newton/m
[D] No units
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Correct Answer: B [poiseiulle]
Notes:
The SI unit of viscosity is poiseiulle (Pl). Its other units are N s m-2 or Pa s.
23. What is the direction of electric and magnetic fields in an electromagnetic wave?
[A] parallel to each other
[B] perpendicular to each other
[C] at 45° to each other
[D] at 120° to each other
Show Answer
Correct Answer: B [perpendicular to each other]
Notes:
Electric and magnetic fields in an electromagnetic wave are perpendicular to each other and to the direction of propagation.
24. What do we call the distance between two consecutive compressions of a sound wave?
[A] Wave number
[B] Frequency
[C] Wavelength
[D] Amplitude
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Correct Answer: C [Wavelength]
Notes:
The distance between two consecutive compressions (C) or two consecutive rarefactions (R) is called the wavelength.
25. What do we call the temperature and pressure at which solid, liquid, and vapor phases of a particular substance coexist in equilibrium?
[A] Equilibrium point
[B] Triple point
[C] Normal point
[D] None of the above
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Correct Answer: B [Triple point]
Notes:
the triple point is the temperature and pressure at which solid, liquid, and vapor phases of a particular substance coexist in equilibrium.
26. What happens when light travels from a denser medium to a rarer medium?
[A] it slows down and bends towards the normal
[B] it speeds up and bends towards the normal
[C] it slows down and bends away from the normal
[D] it speeds up and bends away from the normal
Show Answer
Correct Answer: D [it speeds up and bends away from the normal]
Notes:
A ray of light travelling from a rarer medium to a denser medium slows down and bends towards the normal. When it travels from a denser medium to a rarer medium, it speeds up and bends away from the normal.
27. What do we call the long-sightedness caused by loss of elasticity of the lens of the eye?
[A] Myopia
[B] Presbyopia
[C] Hypermetropia
[D] None
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Correct Answer: B [Presbyopia]
Notes:
Presbyopia is the long-sightedness caused by loss of elasticity of the lens of the eye, occurring typically in middle and old age.
28. What do we call a cell that induces a spontaneous redox reaction to create a flow of electrical charges?
[A] Voltaic cell
[B] Electrolytic cell
[C] Such cells don’t exist
[D] None of the above
Show Answer
Correct Answer: A [Voltaic cell]
Notes:
A Galvanic cell or Voltaic cell induces a spontaneous redox reaction to create a flow of electrical charges, or electricity.
29. What happens to a bar magnet of dipole moment (m) is placed in a uniform magnetic field (B)?
[A] the force on the bar magnet is zero
[B] the torque on the bar magnet is m × B
[C] Both a and b
[D] None of the above
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Correct Answer: C [Both a and b]
Notes:
When a bar magnet of dipole moment m is placed in a uniform magnetic field B: (a) the force on it is zero, (b) the torque on it is m × B, (c) its potential energy is –m.B, where we choose the zero of energy at the orientation when m is perpendicular to B.
30. Which of the following theories is the outcome of mass-energy relation?
[A] General theory of relativity
[B] Field theory of energy
[C] Quantum theory
[D] Special theory of relativity
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Correct Answer: D [Special theory of relativity]
Notes:
The special theory of relativity explains how space and time are linked for objects that are moving at a consistent speed in a straight line. This theory of relativity is experimentally well-confirmed physical theory regarding the relationship between space and time.
