Physics (Part-VI) (Railway)

Total Questions: 50

11. Which of the following devices is based on the principle of electromagnetic induction? [RRB Group 'D' CBT Exam. 23.08.2022 (Shift-III)]

(1) Electric motor
(2) Electric fan
(3) Electric bulb
(4) Electric generator

Correct Answer: (4) Electric generator

Solution:Electric generator is based on the principle of electromagnétic Induction.

• Electromagnetic induction is the phenomenon in which an emf is induced in the coil if there is any change in the magnetic flux linked to the coil.

• In a generator, a coll is rotated in a magnetic field, due to which magnetic flux linked with the coil changes and induces an Electromotive force (EMF).

12. Which of the following statements is/are correct? [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(A) Resistance is independent of temperature.

(B) The more the voltage across a conductor, the more is the resistance.

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

Correct Answer: (3) Only C

Solution:Resistivity is indirectly proportional to the temperature. In other words, as we Increase the temperature of materials, their resistivities will decrease.

• Resistance only depends on the shape, size, and material of the conductor. Increasing the voitage does not affect the resistance.

13. The component of white light that has maximum refractive index is: [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(1) red
(2) yellow
(3) violet
(4) green

Correct Answer: (3) violet

Solution:Refractive index depends upon the wavelength of light.

• Light with the least wave-length is refracted the most (violet- maximum refractive Index.

• while the light with the maximum wavelength is refracted the least (red- least refractive index.)

14. A 2Ω resistance is connected to a 4Ω resistance in series. Their equivalent resistance will be: [RRB Group 'D' CBT Exam, 23.08.2022 (Shift-III)]

(1) 4/3Ω
(2) 3/4Ω
(3) 6Ω
(4) 1Ω

Correct Answer: (3) 6Ω

Solution:The total resistance of a series circuit is equal to the sum of all the individual resistances in the circuit. It is expressed as R = R1 + R2

• So, according to the question, R = 2+4=6Ω

15. The phenomenon due to which the relative motion between a conductor and a magnet produces a potential difference across the conductor is called: [RRB Group D CBT Exam, 23.08.2022 (Shift-III)]

(1) electrostatic force
(2) electromagnetism
(3) electromagnetic force
(4) electromagnetic induction

Correct Answer: (4) electromagnetic induction

Solution:Electromagnetic induction is a phenomenon in which an emf is generated if there is a change in the magnetic flux through a closed-loop.

• When there is relative motion between a magnet and the coil, magnetic flux changes, and hence an electromotive force is generated in the coil.

• This electromotive force generates induced current.

16. A boy standing in front of a magic mirror combination finds his head enlarged, body of same size and legs smaller in size. The mirrors used in the top, middle and bottom of the magic mirror arrangement in the respective order are: [RRB Group 'D' CBT Exam, 23.08.2022 [Shift-III)]

(1) concave, plane, convex
(2) concave, convex, plane
(3) convex, concave, plane
(4) convex, plane, concave

Correct Answer: (1) concave, plane, convex

Solution:The image of head is bigger. This means that the mirror must be a concave mirror. A concave mirror produces an enlarged and erect mirror.

• The middle portion of his body is unaltered and hence the mirror must be a plane mirгог.

• His legs are smaller. The Image is smaller since it is produced by a convex mirror. The convex mirror produces the erect and diminished image.

17. What will be the angle of incidence for a ray of light incident along the principal axis of a convex mirror? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(1) 60°
(2) 90°
(3) 0°
(4) 30°

Correct Answer: (3) 0°

Solution:According to laws of reflection, the angle of incidence is equals to angle of reflection.

• By the question, the incident ray and the reflected ray lies on the same line. Hence, the angle of incidence and the angle of reflection are equal to zero.

• This is possible when the light passes through the principal axis.

18. A convex lens forms a real, inverted and diminished image. The position of the object is: [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(1) at infinity
(2) between F and 2F
(3) between O and F
(4) beyond 2F

Correct Answer: (4) beyond 2F

Solution:A convex lens forms a real, inverted, and diminished image when the object is placed at a distance more than twice the focal length of the lens.

• The image forms on the other side of the lens between F and 2F.

19. A current of 2.5 mA flows through a conductor having resistance 2Ω. The potential difference across the ends of the conductor is: [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(1) 5V
(2) 1.25 V
(3) 5 mV
(4) 1.25 mV

Correct Answer: (3) 5 mV

Solution:According to Ohm's law, the current. I. flowing through a circuit is directly proportional to the voltage, V, and inversely proportional to the resistance, R. it is also expressed as I = V/R, where I is current in ampere, V is potential difference in volt and R is resistance in ohm.

• From the above equation, V = 1 x R

• According to the question, I = 2.5 mA; and R = 2 ohm. So, V=2.5 x 2 = 5 mV

20. A ray of light travelling in air enters a glass slab. Which of the following statement is/are correct? [RRB Group 'D' CBT Exam, 24.08.2022 (Shift-I)]

(i) Angle of incidence is greater than the angle of refraction.

(ii) Angle of incidence is equal to angle of emergence.

(iii) The emergent ray is parallel to the incident ray.

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

Correct Answer: (3) (i), (ii) and (iii)

Solution:Glass is denser medium then air, So when light ray pass from air to glass. ray will bend towards the normal. So, the Angle of refraction is less than the angle of incidence.

• For a rectangular glass slab, the angle of emergence for a ray of light is equal to the angle of incidence. These angles will not be equal when the sides of the glass slab are not parallel.

• In refraction of light through a rectangular glass slab, the emergent ray is parallel to the direction of the incident ray.

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