Physics | Technical Stream | Question Paper 2081-2024 of Class 12 | NEB

Group 'A' [11x1=11]

Rewrite the correct option of each questions in your answer sheet.

1. The time period of simple pendulum is T. If length is made 9 times and mass of the bob is made 4 times then the value of time period becomes

(A) 3
(B) 3T/2
(C) 4T
(D) 2T

2. The radius of gyration of a uniform rod of length l, about an axis passing through its center of mass and perpendicular to its plane is

(A) l/12
(B) l/√2
(C) l/√3
(D) l/√12

3. A liquid does not wet the surface of a solid if the angle of contact is

(A) Zero
(B) Less than 90°
(C) Greater than 90°
(D) Equal to 45°

4. In which thermodynamic process, pressure remains constant ?

(A) Isothermal
(B) Isobaric
(C) Isochoric
(D) Adiabatic

5. The distance between two particles in a wave motion in the out of phase in terms of wave length (l) is

6. The phenomenon of bending of light waves around the corners of obstacles is called

(A) Interference
(B) Diffraction
(C) Polarization
(D) Dispersion

7. Kirchhoff's voltage law is based on the conservation of

(A) mass
(B) charge
(C) energy
(D) angular momentum

8. The value of magnetizing field (H) when magnetic flux density (B) is zero, is called

(A) Retentivity
(B) Curie's temperature
(C) Coercivity
(D) Susceptibility

9. If an electron enters uniform magnetic field B making an angle 300 with the direction of magnetic field, then the path of electron will be

(A) circular
(B) parabolic
(C) helical
(D) straight line

10. Which of the following represents correctly the variation of stopping potential (VO) with the frequency (f) of incident radiation ?

11. In Bohr's atomic model, what is the ratio of speed of an electron in second excited state to that at first excited state ?

(A) 1:2
(B) 2:1
(C) 2:3
(D) 3:2

Group 'B' [8x5=40]

12. a) Define angular momentum. Also write its SI unit and dimension.   [2]

b) A child stands at the centre of turntable with his two arms stretched. The turntable is set rotating with an angular speed of 40 rpm. What is the angular speed of the child if he folds his hands and moment of inertia reduces to 2/3 times the initial value ? [2]

c) What are the analogue of mass and force in rotational motion ? [1]
Or
a) What is mass spring system ?  [1]
b) Show that the oscillation of mass suspended from helical spring is simple harmonic motion. [3]
c) What will be the change in time period of a loaded spring when taken to the moon ? Justify.  [1]

13. a) Define coefficient of viscosity. Also write its unit and dimension. [2]

b) An air bubble of radius 2 mm is rising through a liquid of density 0.82 gmcm⁻³. The coefficient of viscosity of liquid is 349 poise. Neglecting the density of air, calculate the terminal velocity of the air bubble. [3]

14. a) State the first law of thermodynamics. [1]

b) Why gas has two specific heat capacities ? Explain. [1]

c) Derive a relation, Cp - Cv = R, where symbols have their usual meanings.[3]

15. a) Define rectifier. [1]

b) Describe the construction and working of a full wave rectifier. [4]

16. a)   What are X-rays ? Write any two uses of it. [2]

b) Calculate the minimum potential difference between the filament and target of an X-ray tube if tube is to produce X-rays of wavelength of 0.150 nm. [2]

c) How will you control intensity of X-rays ? [1]

17. a) Can two independent sources of light produce interference ? Justify. [1]

b) Write the required conditions for sustained interference of light. [2]

c) In a Young's double slit interference pattern, the slits are 0.2mm apart and the screen is at a distance of 1m. The third bright fringe is found at 9.49mm from the central fringe. Calculate the wavelength of light used. [2]

18. a) State and explain Kirchhoff's Laws of electrical circuits. [2]

b) In the circuit shown in figure, using Kirchhoff's laws. Calculate : (See fig. below:) [3]

i) the current in the 6Ω resistor
ii) the unknown resistance R1
iii) the unknown emf E3
Or
a) State the principle of potentiometer. [1]
b) Derive an expression of an internal resistance of a cell using the principle of potentiometer. [4]

19. a) State and explain Biot-Savart's law. [2]

b) Derive an expression for magnetic field intensity at any point due to a long straight current carrying conductor. [3]

Group 'C'    [3x8=24]

20. a) How are stationary waves formed ? Explain.  [2]

b) Show that the distance between any two consecutive nodes in a stationary wave is λ/2 . [3]

c) What is the effect of temperature on the velocity of sound in a gas ? [1]

d) At what temperature, the velocity of sound in air is increased by 50% to that at 27° C ? [2]
Or
a) The diagram shows a standing wave in a closed organ pipe. (See fig. below:)

i) Define an organ pipe. [1]
ii) How many nodes and antinodes are present in the given standing wave ? [1]
iii) Derive the frequency of above mode of vibration. [2]

b) Write any two differences between intensity and loudness. [1]

c) A source of sound produces sound waves which travels with a speed of 340 ms^-1. The frequency of the source is 500 Hz. Calculate the frequency of sound heard if both source and observer are moving towards each other with a speed of 30 ms⁻¹. [3]

21. a) Define specific charge. Calculate its value for an alpha particle. [2]

b) Show that the path of an electron moving through a transverse uniform electric field is parabolic. [3]

c) If ultraviolet rays and X-rays are incident on a metal surface, in which case greater stopping potential is measured ? Justify. [2]

d) Draw a graph showing the variation of photoelectric current with the intensity of incident light on a metal surface. [1]

22. a) Define r.m.s. value of an alternating current. [1]

b) Why 220V ac is more dangerous than 220V dc ? Justify. [2]

c) An alternating emf is applied across a capacitor. Show that the current in it leads to the applied emf by π/2 . [3]

d) A 2.5 μf capacitor is connected in series with a resistor of resistance 300 Ω across a 50V, 1000/2π Hz ac source. Calculate the impedance of the circuit. [2]

Physics Technical Stream Question Paper 2081-2024 of Class 12 NEB.

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