Physics (Part-III) (Railway)

Total Questions: 50

21. The change of vapor into liquid (water) is called which physical action? [RRB RPF/RPSF SI Exam, 13.01.2019 Shift-III]

(1) Sublimation
(2) Condensation
(3) Precipitation
(4) Evaporation

Correct Answer: (2) Condensation

Solution:Condensation is the change in phase of a gas upon the surface of a solid due to its loss of energy to that solid. Water droplets often form on the surface of cool substances because the water vapor in the air loses energy when it comes into contact with the cold substance and turns to a liquid

22. What is the full form of 'TIR' in the light? [RRB RPF/RPSF SI Exam, 13.01.2019 Shift-III]

(1) Total Internal Radiation
(2) Total Internal Reflection
(3) Total Intellectual Reflection
(4) Total Internal Reduction

Correct Answer: (4) Total Internal Reduction

Solution:Total internal reflection (TIR) is complete reflection of a ray of light within a medium such as water or glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle.

23. The formula for finding the tension (in weight) is: [RRB RPF/RPSF SI Exam, 13.01.2019 Shift-III]

(1) force/area
(2) force/mass
(3) force/time
(4) mass/area

Correct Answer: (1) force/area

Solution:Stress is the external restoring force acting on per unit area. Stress is denoted by o. It is represented as N/m2.

24. ........ is a plane of constant potential whose potential is fixed at each point. [RRB RPF/RPSF SI Exam, 16.01.2019 Shift-II]

(1) Numerical potential plane
(2) Multiple potential plane
(3) Even plane
(4) Equipotential plane

Correct Answer: (4) Equipotential plane

Solution:All points on an equipotential surface have the same electric potential (i.e. the same voltage). The electric force neither helps nor hinders motion of an electric charge along an equipotential surface. Electric field lines are always perpendicular to an equipotential surface.

25. When the driving force on the oscillator becomes equal to the actual frequency of the oscillator, the increase in the amplitude of the oscillator is called- [RRB RPF/RPSF SI Exam, 16.01.2019 Shift-II]

(1) Induced frequency
(2) Resonance
(3) Free amplitude
(4) Induced amplitude

Correct Answer: (2) Resonance

Solution:Resonance is a phenomen on in which an external force or a vibrating system forces another system around it to vibrate with greater amplitude at a specified frequency of operation. The frequency at which the second body starts oscillating or vibrating at higher amplitude is called the resonant frequency of the body.

26. What is the minimum amount of energy required for the release of an electron from the surface of metal called? [RRB RPF/RPSF SI Exam, 16.01.2019 Shift-II]

(1) Work function
(2) Workforce
(3) Work Emission
(4) Work Energy

Correct Answer: (1) Work function

Solution:The minimum energy required or needed to remove an electron from the surface of the metal is called the Work Function of a Metal. This can be defined with photoelectric effect. The energy or the work function removes an electron from a solid to a point in the vacuum, immediately outside the solid surface.

27. The number of collisions per second per unit volume of a mica mixture is called? [RRB RPF/RPSF SI Exam, 16.01.2019 Shift-II]

(1) Collision displacement
(2) Collision velocity
(3) Collision Force
(4) Collision Frequency

Correct Answer: (4) Collision Frequency

Solution:Collisional Frequency is the average rate in which two reactants collide for a given system and is used to express the average number of collisions per unit of time in a defined system.

28. The relative motion between two surfaces in contact is________ due to friction. [RRB RPF Constable Exam, 17.01.2019 Shift-III]

(1) Involved
(2) Increases
(3) No results
(4) Static friction

Correct Answer: (4) Static friction

Solution:The friction that exists be tween two surfaces in contact. when there is no relative speed between them is called static friction.

Only when the relative motion begins does sliding friction begin to act.

It acts on both surfaces in contact of equal magnitude and opposite directions.

29. What is the unit of relative density? [RRB RPF Constable Exam, 17.01.2019 Shift-III]

(1) No Unit
(2) kg m-¹
(3) kg m-²
(4) kg m-³

Correct Answer: (1) No Unit

Solution:Relative density is the ratio of the density of a substance to the density of water at 4°C.

• As relative density is the ratio of same quantities. It is a dimensionless quantity and has no unit.

30. Which of the following phenomena deals with dispersion of light due to dust particles and air? [RRB RPF Constable Exam, 17.01.2019 Shift-III]

(1) Tyndall Effect
(2) Peltier Effect
(3) Seebeck Effect
(4) Raman Effect

Correct Answer: (1) Tyndall Effect

Solution:The Tyndall effect is the effect of light scattering in colloidal dispersion, while showing no light in a true solution. This effect is used to determine whether a mixture is a true solution or a colloid.

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