Physics | Grade XII | Exam Paper 2074 [2017] | National Examinations Board

NATIONAL EXAMINATIONS BOARD [NEB]
Physics - Grade XII
Examination - 2074 (2017)
Regular Students | Subject Code: 210 ‘A’
Time - 3 hrs
Full Marks - 75
Pass Marks - 27
DOWNLOAD PDF | of Exam Paper | PHYSICS | Grade XII | 2074 [2017] NEB
Candidates are required to give their answers in their own words as far as practicable. The figures in the margin indicate full marks.

Attempt all the questions:


Group 'A'

1. Answer, in brief, any four questions: [4x2=8]

a) You are given n wires, each of resistance R. What is the ratio of maximum to minimum resistance obtainable from these wires?
b) Why do we prefer a potentiometer to measure emf of a cell rather than a voltmeter?
c) What is angle of dip? How is it related with components of earth's magnetic field?
d) Why is soft iron used to make core of transformer?
e) If the number of turns of a solenoid is doubled, keeping the other factors constant, how does the self inductance of the solenoid change?
f) The emf of an ac source is given by the expression, E=300 sin 314t volts. Write the values of peak voltage and frequency of source.

2. Answer, in brief, any four questions. [4x2=8]

a) Why is neutron considered the most effective bombarding particle in nuclear reaction?
b) The value of e/m is constant for cathode rays but not for positive rays, why?
c) The output of two-input AND gate is fed to a NOT gate. Give its logic symbol and write down it's truth table. Identify the new logic gate formed.
d) How does a daughter nucleus differ from its parent nucleus when it emits i) an α-particle and      ii) a β-particle?
e) State Hubble's Law and write the significant of Hubble's constant.
f) What is energy crisis? Explain.

3. Answer, in brief, any one question. [2]

a) Longitudinal waves are called pressure waves. Why?
b) What is the threshold of hearing? Define one bel.

4. Answer, in brief, any one question. [2]

a) Explain with proper skecth, the differences between wavefronts and wavelets.
b) What is polarizing angle? Does it depend on wavelength of light used?

Group 'B'

5. Answer any three questions:  [3x4=12]

a) Describe the mechanism of current flow in a conductor and derive a relation between current density and drift velocity of electrons.
b) What is Seebeck effect? Explain the variation of thermo emf with gradual increase in the temperature of hot junction, keeping the cold junction at 0°C.
c) State Biort-Savart Law. Use this law to find the magnetic field due to a current carrying circular coil at any point on the axis of the coil.
d) State and explain Faraday's Law of electromagnetic induction. Obtain an expression for the emf induced in the rectangular coil rotating in a uniform magnetic field.

6. Answer any three questions: [3x4=12]

a) What is zener diode? Explain its use as a voltage regulator.
b) Discuss photoelectric effect and derive Einstein's photoelectric equation. What is stopping potential?
c) Define mass defect and binding energy of a nucleus. Draw a graph showing the variation of binding energy per nucleon and atomic number of the elements. Also interpret the graph.
d) Explain renewable and non-renewable sources of energy with examples. Give an account of the energy consumption scenario in Nepal.

7. Answer any one question: [4]

a) Describe Newton's formula for the velocity of sound in air. Explain why and how this formula is modified by Laplace.
b) Describe an experiment with the necessary theory by which the speed of sound in air is determined by using resonance tube method.

8. Answer any one question: [4]

a) Define coherent sources of light. Prove that the dark and bright fringes are equally spaces in Young's double slit experiment.
b) What is diffraction grating? Discuss the formation of diffraction pattern due to a diffraction grating.

Group 'C'

9. Answer any two question: [2x4=8]

a) What must be the emf E in the circuit so that the current flowing through the 7Ω resistor is 1.80A? Each emf source has negligible internal resistance.
emf in the Circuit
b) A straight horizontal rod of length 20 cm and mass 30 gm is placed in uniform horizontal magnetic field perpendicular to the rod. If a current of 2A through the rod makes itself supporting in the magnetic field, calculate the magnetic field.
c) A coil of inductance 0.1H and negligible resistance is in series with a resistance 40Ω. A supply voltage of 50V (rms) is connected to them. If the voltage across L is equal to that across R, calculate the voltage across the inductor and frequency of the supply. 

10. Answer any two question: [2x4=8]

a) An acceleration moves in a circular path of radius 20 cm in a uniform magnetic field of 2x10-3 r. Find the speed of the electron and period of revolution.  Mass of electron = 9.1x10-31 Kg.
b) Calculate the Broglie wavelength of an electron which has been accelerated through a potential difference of 200V. Given-mass of electron= 9.1x10-31 Kg and Planck's constant h=6.6x10-34 JS.
c) The isotope Ra-226 undergoes α decay with a half life of 1620 years. What is the activity of 1g of Ra-226? Avogadro number = 6.03x1023 /mole.

11. A car is approaching towards a cliff at a speed of 20 m/s. The driver sounds a whistle of frequency 800 Hz. What will be the frequency of the echo as heard by the car driver? Velocity of sound in air = 350 m/s. [4]

12. A plane mirror is placed at the centre of a concave mirror having radius of curvature 40 m. The plane mirror rotates at the speed of 2600 revolutions per second. Calculate the angle between a ray incident on the plane mirror and then reflected from it after the light has travelled to the concave mirror and back to the plane mirror. Given speed of light is 3x108m/s. [3]

View/see Grade 12 Question Paper of Physics 2074/2017 NEB:
NEB Class 12 Physics Question Paper 2074-2017

NEB Class 12 Physics Question Paper 2074-2017

NEB Class 12 Physics Question Paper 2074-2017

NEB Class 12 Physics Question Paper 2074-2017
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