Physics (Part-II) (Railway)

Total Questions: 50

21. What happens to the ammeter reading when the length of the wire is doubled? [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) It increases two times
(2) It decreases to one half
(3) It decreases to three-fourth
(4) It remains the same

Correct Answer: (2) It decreases to one half

Solution:Electrical resistivity is the property of the material independent of the geometry of conductor. It is basically resistance for a given area of cross-section of conductor per unit length. When length of wire is doubled, the resistance is also doubled, because resistance is directly proportional to length of wire. Hence according to ohms law for a given potential difference, the current reduces to half.

22. Which of the following has NO unit? [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) Density
(2) Relative density
(3) Displacement
(4) Pressure

Correct Answer: (2) Relative density

Solution:Relative density is a ratio of the density of a certain material to the density of a reference material. It has no unit, because the units of the material in question cancel out with the units of the reference material.

23. The energy possessed by a body due to its change in position or shape is called: [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) kinetic energy
(2) chemical energy
(3) nuclear energy
(4) potential energy

Correct Answer: (4) potential energy

Solution:The energy possessed by a body on account of its position or configuration (shape and size) is called potential energy. For example, water stored in a dam has large amount of potential energy due to its height above the ground. A stretched rubber band possesses potential energy due to its distorted shape.

24. In a hydro-electric power station ultimately which energy is converted into electrical energy? [RRB ALP & Technician Exam, 29.08.2018 Shift-I]

(1) Mechanical energy
(2) Potential energy
(3) Heat energy
(4) Kinetic energy

Correct Answer: (4) Kinetic energy

Solution:Hydropower plants capture the energy of falling water to generate electricity. A turbine converts the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy.

25. When a bullet is fired from a gun, Its potential energy is converted into: [RRB ALP & Technician Exam, 29.08.2018 Shift-III]

(1) kinetic energy
(2) mechanical energy
(3) heat energy
(4) chemical energy

Correct Answer: (1) kinetic energy

Solution:A bullet stores chemical potential energy in its gunpowder. When the bullet is fired, this potential energy is converted into kinetic energy and heat.

26. With a Concave mirror (Centre of curvature), when an object is placed at the Focus (F), which of the following applies for the image? [RRB ALP & Technician Exam, 29.08.2018 Shift-III]

(1) Real, inverted, highly diminished image of F.
(2) Real, inverted image of the same size at C.
(3) Real, inverted, highly enlarged image at infinity.
(4) Real, inverted, diminished image between C and F.

Correct Answer: (3) Real, inverted, highly enlarged image at infinity.

Solution:In a concave mirror, when the object is placed at the principal focus, then the parallel ray of light passes through the principal focus F giving the reflected ray parallel to the principal axis and the second ray of light passing through the centre of curvature C is reflected along the same path forming the reflected ray. In this case, both the reflected rays become parallel to each other so these rays cannot intersect each other and the image will be formed at infinity. The image formed in this case will be highly enlarged, real and inverted.

27. The state of matter can be changed into another state by changing the: [RRB ALP & Technician Exam, 30.08.2018 Shift-I]

(1) Volume
(2) Density
(3) Shape
(4) Temperature

Correct Answer: (4) Temperature

Solution:The physical state of matter can be changed in two ways: by changing temperature (heating or cooling) or changing pressure(increasing or decreasing). For example, when ice (a sold) is heated, it changes to water (a liquid). This change is called melting. If water is heated, it changes to steam (a gas) through evaporation.

28. While releasing the arrow from a stretched bow, the potential energy of the bow is converted into? [RRB ALP & Technician Exam, 30.08.2018 Shift-I]

(1) chemical energy
(2) kinetic energy
(3) sound energy
(4) heat energy

Correct Answer: (2) kinetic energy

Solution:A stretched bow has potential energy due to the change in its shape. To shoot the arrow, the bow has to be released. Therefore, its potential energy is converted into the kinetic energy. The arrow gains its kinetic energy from the elastic potential energy which gets stored in the string of the bow when we stretch it.

29. What is the range of frequencies of sound waves audible to human beings? [RRB ALP & Technician Exam, 30.08.2018 Shift-I]

(1) 16 kHz to 200 kHz
(2) 16 Hz to 16 kHz
(3) 16 Hz to 20 kHz
(4) 14 Hz to 20 kHz

Correct Answer: (3) 16 Hz to 20 kHz

Solution:Human range is commonly given as 20 Hz to 20,000 Hz, although there is considerable variation between individuals, especially at high frequencies. Under ideal laboratory conditions, humans can hear sound as low as 12 Hz and as high as 28 kHz.

30. Mechanical energy is equal to: [RRB ALP & Technician Exam, 30.08.2018 Shift-I]

(1) Kinetic energy + Chemical energy
(2) Kinetic energy + Potential energy
(3) Kinetic energy + Heat energy
(4) Kinetic energy + Electrical energy

Correct Answer: (2) Kinetic energy + Potential energy

Solution:In physical sciences, mechanical energy is the sum of potential energy and kinetic energy. It is the energy associated with the motion and position of an object. The principle of conservation of mechanical energy states that in an isolated system that is only subject to conservative forces, the mechanical energy is constant.

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