Physics (Part-VI) (Railway)

Total Questions: 50

21. Electromagnetic induction was discovered by: [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(1) Michael Faraday
(2) Alessandro Volta
(3) Isaac Newton
(4) Albert Einstein

Correct Answer: (1) Michael Faraday

Solution:On August 29 in 1831, British scientist Michael Faraday discovered electromagnetic induction.

• He discovered that that a change in a magnetic field produces an electromotive force and current in a nearby circuit.

• This phenomenon, called electromagnetic induction, was later mathematically modelled by James Clerk Maxwell, and came to be known as Faraday's Law.

22. Which of the following is NOT a unit of power ? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(1) kilowatt hour
(2) watt
(3) joule/second
(4) horsepower

Correct Answer: (1) kilowatt hour

Solution:The kilowatt-hour (symbolized kWh) is a unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour (1 h) of time.

• The kilowatt-hour is not a standard unit in any formal system, but it is commonly used in electrical applications.

23. In which of the following case(s) will a current be registered by the galvanometer connected to a circular coil? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(i) When a magnet is held stationary near the coil.

(ii) When a magnet is moved towards the coil.

(iii) When a magnet is moved away from the coil.

(1) Both (ii) and (iii)
(2) Only (iii)
(3) Both (i) and (ii)
(4) Only (i)

Correct Answer: (1) Both (ii) and (iii)

Solution:The induced current forms in a galvanometer when the magnet is moved away or pushed towards its axis.

• Due to the phenomena of electromagnetic induction, when a magnet is moved toward or away from the coil, a current is induced in the coil.

24. If a coil of a conductor with 50Ω resistance 19 subjected to time varying magnetic field such that the EMF induced is 5V, then the induced current in the coil is: [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-II)]

(1) 0.1A
(2) zero
(3) infinite
(4) 0.01A

Correct Answer: (1) 0.1A

Solution:∈/R = 5V/50Ω = 1/10 A = 0.1A

25. The value of absolute refractive index of a medium is always: [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-II)]

(1) equal to 0
(2) more than 1
(3) equal to 1
(4) less than 1

Correct Answer: (2) more than 1

Solution:The absolute refractive index (n=c/v) of any medium is always greater than 1.

• This is because speed of light in any medium is always less than that in vacuum (i.e v<c).

26. A ray of light is incident on the pole of a concave Mirror. The acute angle between the Incident ray and the principal axis will be called: [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-II)]

(1) angle of emergence
(2) angle of reflection
(3) angle of deviation
(4) angle of incidence

Correct Answer: (4) angle of incidence

Solution:In Physics, the angle of Incidence is the angle formed in between a ray propagated on a surface and the line normal to the point of occurrence on the same surface.

• When ray of light is made to fall on the pole of a concave mirror, the angle of reflection Is same as the angle of inchdence at the pole.

27. Which among the following mirror(s) always forms virtual and erect image? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-II)]

(A) Convex mirror

(B) Plane mirror

(1) Only B
(2) Only A
(3) Both A and B
(4) Both B and C

Correct Answer: (3) Both A and B

Solution:A plane mirror always gives a virtual and erect image of the object but the size of the image is the same as the size of the object.

• A concave mirror does not always give a virtual and erect image. When the object is placed between focus and pole, the image is virtual, erect, and magnified.

• A convex mirror always gives a virtual and erect image of the object and the size of the image is smaller than the size of the object.

28. Which of the following materials is preferably used for electrical transmission lines? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-II)]

(1) Copper
(2) Nichrome
(3) Tin-lead alloy
(4) Tungsten

Correct Answer: (1) Copper

Solution:Copper wires are generally used for electrical power transmission.

• This is because copper is a good conductor and has bery low resistivity.

• The electrical conductivity of copper is almost as good as silver.

29. A beam of white light under goes dispersion through a triangular glass prism forming a band of seven colours. Which of the statements is/are correct? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-II)]

(a)The red-coloured component has minimum refractive index

(b) The violet coloured component deviates the least

(1) Only (a)
(2) Both (b) and (c)
(3) Both (a) and (b)
(4) Only (b)

Correct Answer: (1) Only (a)

Solution:During the dispersion of white light into different colours, the scattering of light depends on the wavelength of the light.

• Violet colour refracts the most because violet light in the visible light spectrum has a smaller wavelength of about 400 nanometers when compared to red at 650 nanometers.

• During dispersion of white light by a prism, different colors travel with different speed hence they split in prism.

• Red travels the faster while violet travels slowest so Red is on top and violet is at bottom.

30. A current of 5A flows through an electrical appliance when the potential difference of 50V is applied across its terminals. What will be the current drawn by the appliance if the potential difference is increased to 110V? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-II)]

(1) 10A
(2) 25A
(3) 5A
(4) 11A

Correct Answer: (4) 11A

Solution:V = 50V , I = 5A, R = V/I

= 50/5 = 10 Ω

When P. D increased to 110V

I = V/R = 110/10 = I I A.

∴ The Current through the heatesr become 11A

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