Physics (Part-VII) (Railway)

Total Questions: 50

11. Two resistors, A of 8Ω and B of 12Ω, are connected in series with a battery of 6V. If V₁ and V₂ are the potential drops across A and B I₁, and I₂ are the currents through them, respectively, then (V₁/V₂) and (I₁/I₂) are respectively________. [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-I)]

(1) (3/2) and (2/3)
(2) (2/3) and 1
(3) (2/3) and 1
(4) (2/3) and (3/2)

Correct Answer: (3) (2/3) and 1

Solution:Ω

Since both resistors are in series

∴ I = 6/8 + I2 = 6/20 = 3/I0 A

∴ I I = I2 = I = 3/I0A

∴ I₁/I₂ = I

Now

V₁ = Potential drops across A

= I * 8 = 12/5 V

V₁ = A

V₂ = Potential drops across B

= I * I2 = 3/10 * 12 = 18/5 V

∴ V₁/V₂ = I2/5/I8/5 = 12/I8 2/3

12. Red colour is scattered the___ by fog or smoke because its wavelength is _ than the wavelength of other colour components of white light [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-I)]

(1) least, less
(2) least more
(3) most, more
(4) most, less

Correct Answer: (2) least more

Solution:The red light has the largest wavelength among all visible parts of light and so it is scattered the least by the fog of smoke.

• Scattering of light is more effective in blue, yellow, and green due to their shorter wavelengths.

13. When a 24 V potential is applied across a conductor and 96 mA current is flowing through it then the resistance of the conductor is: [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) 250 Ω
(2) 0.250 Ω
(3) 40 Ω
(4) 0.40 Ω

Correct Answer: (1) 250 Ω

Solution:Electric potential (V), current (I) and resistance (R) are related as V=IR or R = V/I

• According to the question, V = 24V and 1=96mA or 0.096A

• So, R =24/0.096 = 250 Ω

14. An object of size 1.0 cm is placed in front of a concave mirror of focal length 16 cm, at a distance of 24 cm. The image formed is_ and its height is__. [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) inverted, 2.0 cm
(2) erect, 0.4 cm
(3) erect, 2.0 cm
(4) inverted, 0.4 cm

Correct Answer: (1) inverted, 2.0 cm

Solution:From the question, u (object distance) = -24 cm; f = 16 cm; h = 1cm

From mirror formula: 1/f=1/u+1/v, where v = image distance 1/v= 1/f =1/u= /1/-16-1/-24=1/-48

So, v= -48 cm

The image is formed at a distance of 48 cm on the left side of the mirror from the pole.

Now, magnification m = h'(height of image)/h height of object)= -v/u or h' = -1 x-48/-24= -2 cm So, the image size is 2 cm, and it is real and inverted.

15. When resistors are connected in series combination, then potential difference across each resistor will be: [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) Proportional to thickness
(2) Proportional to resistance
(3) Equally divided
(4) Similar

Correct Answer: (2) Proportional to resistance

Solution:In case of series combination, the total or equivalent resistance has the same effect on the circuit as the original combination of resistors as it is the algebraic sum of the Individual resistances.

• In such a circuit, total supply voltage across the resistors is equal to the sum of the potential differences across.

• The circuit splits the supply voltage proportionally across each resistor.

16. Which of the following CANNOT be explained using the phenomenon of scattering of light? [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) Red colour used for dan. ger signals
(2) Blue colour of sky
(3) Twinkling of stars
(4) Reddening of sun during sunrise

Correct Answer: (3) Twinkling of stars

Solution:The twinkling of stars is due to atmospheric refraction of light. The atmosphere is made of several layers and the refractive indices keep on changing continuously.

• As a result, the path of light rays from the star keeps on changing their path continuously.

• So, the number of rays entering, the pupil of eye goes on changing with time and the stars appear twinkling.

17. An optical device X forms an image CD for an object AB as shown in the figure. The device X is a: [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) convex lens
(2) convex mirror
(3) concave mirror
(4) concave lens

Correct Answer: (3) concave mirror

Solution:In case of Concave mirror, when the object is placed between Pole (P) and Focus (F). the rays form an image behind the mirror. So, the image is virtual.

• And the image formed would be larger than the object (magnified) and is erect.

18. How much energy is released when water is used to break down the terminal link of ATP? [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) 31.5 kJ/mol
(2) 35.6 kJ/mol
(3) 37.2 kJ/mol
(4) 30.5 kJ/mol

Correct Answer: (4) 30.5 kJ/mol

Solution:The energy released during respiration process is used to make an ATP molecule from ADP (adenosine diphosphate) and inorganic phosphate (P).

• When the terminal phosphate linkage in ATP is broken using water, the energy equivalent to 30.5 kJ/mol is released.

19. When magnetic field is acting towards north and current is moving in east to west direction through a conductor, then the conductor will move________ direction [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) towards left
(2) in the downward
(3) in the upward
(4) towards right

Correct Answer: (2) in the downward

Solution:Right-hand thumb rule states that if a current carrying conductor is imagined to be held in the right hand such that the thumb points in the direction of the current, then the curled fingers indicate the direction of the magnetic field.

• If the current flows in the upward direction, then the direction of the magnetic field is clockwise, then the direction facing will be the North Pole.

• If the current flows in the downward direction the direction of the magnetic field is anticlockwise, then the direction facing will be the South Pole.

20. Direction of rotation of armature of motor can be found with the help of________. [RRB Group 'D' CBT Exam, 01.09.2022 (Shift-III)]

(1) Fleming's right-hand rule
(2) Fleming's left-hand rule
(3) Maxwell's corkscrew rule
(4) Right hand thumb rule

Correct Answer: (2) Fleming's left-hand rule

Solution:Fleming's Left-Hand Rule is a simple and accurate way to find the direction of force/motion of the conductor in an electric motor when the magnetic field direction and the current direction are known.

• It is used to find the direction of force or motion acting on the moving coil in the DC motor.

« Previous 123 4 5 Next »