Physics (Part-X) (Railway)

Total Questions: 51

31. Which of the following statements is/are true in case of an incandescent filament bulb? [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(a) Filament can be made of tungsten or nichrome.

(b) The glass envelope covering the filament is filled with inactive gases such as nitrogen or argon.

(d) The resistivity of the filament is low to allow more current.

(1) (a), (b), (e)
(2) (c), (d), (e)
(3) (b), (c), (d)
(4) (a), (c), (d)

Correct Answer: (1) (a), (b), (e)

Solution:The resistance of a light bulb filament is effected by both length and cross-sectional area.

• Thicker wires have less resistance, thinner wires gave higher resistance.

• According to Ohm's law, the current flowing in a circuit is inversely proportional to the resistance of the circuit. So, higher resistance means less current.

32. object is placed___________ to obtain an inverted and enlarged image. [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) between C and F of concave mirroг
(2) between C and F of convex mirror
(3) at infinity from concave mirror
(4) at infinity from convex mirror

Correct Answer: (1) between C and F of concave mirroг

Solution:between C and F of a concave mirroг

• When an object lies between focus and centre of curvature. then a real, inverted and enlarged image is formed by the concave mirror.

• The image is formed beyond the centre of curvature of the concave mirror.

33. A galvanometer when connected in a circuit, detects the presence of: [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) Resistance
(2) Current
(3) Frequency
(4) Potential difference

Correct Answer: (2) Current

Solution:A galvanometer is an electromechanical measuring instrument for electric current.

• It measures a small electrical current or a function of the current by deflection of a moving coil.

•The deflection is a mechanical rotation derived from forces resulting from the current.

34. The power of an electric bulb. of resistance 18 ohm if no voltage is applied across it is_________. [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) 18 W
(2) 9 W
(3) infinity
(4) 0 W

Correct Answer: (4) 0 W

Solution:The relationship between Power and Resistance can be expressed as P = V²/R, where P is the Power and we measure it in watts or W. R is the resistance measured in ohms

• V is the electric potential measured in volt.

• Since, the voltage is 0, power will be 0 watt.

35. The voltages across three resistances R₁, R₂ and R₃ connected in series are V₁, V₂ and V₃, respectively. What is the net voltage V across them if I represents the net current flowing through them? [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) V = (1/V₁) + (1/V₂) + (1/V₃)
(2) V = (1/R₁) + (1/R₂) + (1/R₃)
(3) V = R₁ +R₂ +R₃
(4) V = V₁ + V₂ + V₃

Correct Answer: (4) V = V₁ + V₂ + V₃

Solution:As current passes through each resistor in a series circuit, it establishes a difference in potential across each individual resistance,

• This is commonly called voltage drop, and its magnitude is in direct proportion to the value of resistance.

• Voltage in a series circuit is additive.

• Therefore V (total voltage) = V1 + V2 + V3

36. The SI unit of power of a lens is: [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) newton
(2) dioptre
(3) joule
(4) metre

Correct Answer: (2) dioptre

Solution:Dioptre is unit of power of lens.

• It is equal to the reciprocal of the focal length measured in metres.

• Power of a lens is the ability of a lens to converge or diverge light rays depending on its focal length.

37. Among the following situations, potential difference is induced in a closed conducting coil when: [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) the closed coil is moved towards the bar magnet only
(2) either the bar magnet is moved towards the closed coll or the closed coil is moved towards the bar magnet
(3) both the bar magnet and the closed coil are moving with same speed and in the same direction
(4) a bar magnet is moved towards the closed coil only

Correct Answer: (2) either the bar magnet is moved towards the closed coll or the closed coil is moved towards the bar magnet

Solution:either the bar magnet is moved towards the closed coil, or the closed coil is moved towards the bar magnet.

• Electric potential difference is Induced when there is charge separation in the conductor due to force by magnetic field.

• Potential difference is induced in a closed conducting coil when the bar magnet is moved towards the closed coil, orthe closed coil is moved towards the bar magnet.

38. When a magnet is moved into a coil connected to a galvanometer, the current is induced in the coil. The induced current does not depend on which of the following factor? [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(1) Number of turns of the coil
(2) The pole strengh of the magnet
(3) Speed of movement of the magnet
(4) Resistance of the galvanometer connected in the coil

Correct Answer: (4) Resistance of the galvanometer connected in the coil

Solution:Electromagnetic induction is the production of an electromotive force across a conductor when it is exposed to a varying magnetic field.

• This process of electromagnetic induction, in turn, causes an electrical current it is said to induce the current.

• It depends on number of turns in the coil, Intensity of the magnetic field and relative speed between coil and the magnet but does not depend on the resistance of the coil.

39. From the following, identify the applications of scattering of light. [RRB Group 'D' CBT Exam, 11.10.2022 (Shift-III)]

(a) Danger signals being red

(b) Advanced sun rise and delayed sun set

(d) Tyndall effect

(e) Redness of sun and blue ness of sky

(1) (d), (e), (a)
(2) (c), (d), (e)
(3) (a), (b), (c)
(4) (b), (c), (d)

Correct Answer: (1) (d), (e), (a)

Solution:Some of the applications of Scattering of Light are as follows:

• The sky appears blue as the light gets scattered by the particles present in the atmosphere.

• During sunset and sunrise. the sky appears red due to the scattering of light.

• Red colour scatters the least as it has the greatest wavelength. So red light is able to travel the longest distance through the fog, rain, and air particles. That is why the red colour is used in danger signals.

• Tyndall effect is scattering of light by particles in a colloidal mixture. When rays of light pass through a colloidal fluid, the tiny particles get illuminated due to scattering. Because of this, the path of light is made visible.

40. What type of simple machine is a screwdriver? [RRC NWR Jaipur GDCE ALP Exam, 22.07.2023 (Shift-II)]

(1) inclined plane
(2) wedge
(3) wheel and axle
(4) pulley

Correct Answer: (3) wheel and axle

Solution:A screwdriver is an example of a wheel and axle machine.

• A wheel and axle is a simple machine consisting of two cylinders or discs with different radii.

• Turning one applies an exponential amount of force on the other.

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