Physics (Part-X) (Railway)

Total Questions: 51

1. The phenomena of scattering of light by colloidal particles gives rise to__________. [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-I)]

(1) dispersion
(2) Tyndall effect
(3) Total internal reflection
(4) refraction of light

Correct Answer: (2) Tyndall effect

Solution:The colloidal particles with size (1 nm - 10-⁹m) are enough to scatter a beam of light passing through them.

• This scattering of a beam of light by colloidal particles is called Tyndall effect.

• They continuously show Tyndall effect because the particles remain suspended in the entire solution.

2. The Sl unit of electric power is_________. [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-I)]

(1) Newton
(2) Watt
(3) Joule
(4) Calorie

Correct Answer: (2) Watt

Solution:Electric power is defined as the energy consumed by the electrical appliance per unit time.

• The SI unit of electric power is watt (W).

• It is the power consumed by a device that carries 1 A of current when operated at a potential difference of 1 V.

3. When two resistors are connected in series, their total effective resistance if 12Ω. When the same two resistors are connected in parallel then their effective resistance is 30Ω. The resistances of the two resistors. [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-I)]

(1) 70Ω and 50Ω
(2) 80Ω and 40Ω
(3) 90Ω and 30Ω
(4) 60Ω and 60Ω each

Correct Answer: (4) 60Ω and 60Ω each

Solution:

4. The presence of a magnetic field can be determined by_________. [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-I)]

(1) a voltmeter
(2) a galvanometer
(3) a magnetic needle
(4) an ammeter

Correct Answer: (3) a magnetic needle

Solution:The presence of magnetic field at a point can be detected by a compass needle.

• In the presence of a magnetic field, the needle of compass rests only in the direction of magnetic field and in the absence of any magnetic, field. the needle of the compass can rest in any direction.

5. For a given concave mirror of focal length 0.5 m if the object distance is 0.6 m, then the magnification produced is: [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-I)]

(1) 5
(2) -0.5
(3) 0.5
(4) -5

Correct Answer: (4) -5

Solution:u = 0.6m

f = 0.5

1/f = 1/v + 1/U

⇒ 1/0.5 - 1/0.6 = 1/V

1/0.3 = 1/v

or, v = 3

Magnification (m) = -v/u

= - 30/6 = -5

6. The correct relation between refractive index (u), speed of light in air (c) and speed of light in the medium (v) is: [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-I)]

(2) μ = c/v
(1) 1/μ = c/v
(3) c = μ/v
(4) v= μ/c

Correct Answer: (2) μ = c/v

Solution:Refractive index of a medium is defined as the ratio of the velocity of light in air and the velocity of light in that medium.

• Refractive index, μ = c/v, c is the velocity of light in air and v is the velocity of light in the medium.

7. An example of a series circuit is________. [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-III)]

(1) the wiring system at home
(2) Street lights
(3) car head lights
(4) decoration lights

Correct Answer: (4) decoration lights

Solution:The series circuit is a closed circuit in which cur-rent flows from one path.

• In this setup, the bulbs are connected in such a way that electricity passes from the source to the first bulb/light and then to the second and so on until it reaches the last bulb and then return to the source.

• This type of connection is used in decorative lighting.

8. As the object is moved from the pole towards the focus of a concave mirror, the cоггеsponding image moves from__ and the image is_. [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-III)]

(1) pole to infinity, virtual and erect
(2) infinity to pole, virtual and erect
(3) pole to Infinity, real and inverted
(4) infinity to pole, real and inverted

Correct Answer: (1) pole to infinity, virtual and erect

Solution:pole to infinity, virtual and erect.

• In a concave mirror, when the object is at infinity, the image is formed at the focus or in the focal plane.

• As the object is moved from the pole towards the focus of a concave mirror, the corresponding image moves from pole to infinity.

• When the object is placed between the focus and the pole, the image will be virtual and hence it will be formed behind the concave mirror.

9. For an electric generator. which of the following statement(s) are true: [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-III)]

(i) Induced current can be increased by increasing the number of turns in the coil.

(ii) Induced current can be increased by increasing the speed of the coil.

(iii) Induced current can be increased by decreasing the applied magnetic field

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

Correct Answer: (3) Both (i) and (ii)

Solution:The current produced during electromagnetic induction is called Induced current.

• The magnitude of the induced current can be increased by moving the magnet more quickly into or out of the coil, using a stronger magnet and increasing the number of turns in the coil.

10. The induced emf developed in a conductor when it is moved in a direction parallel to the magnetic field is________. [RRB Group 'D' CBT Exam, 07.10.2022 (Shift-III)]

(1) Infinity
(2) Zero
(3) Maximum
(4) Minimum

Correct Answer: (2) Zero

Solution:Current will be induced in a conductor when there is a change of magnetic flux.

• But, if the conductor is moving parallel to magnetic field. magnetic flux will not change and hence, induced current will not be developed.

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