National Examinations Board Grade 12 Physics — Grade Increment (Supplementary) 2080 (2023) (Set A)

National Examinations Board · Physics (Grade 12) · 2080 (2023) BS · Grade Increment (Supplementary) Examination — 22 questions — a free old question paper on Goodone.club’s exam-paper archive.

  1. The moment of inertia of a body of mass M about a given axis is I. What is the radius of gyration? (A) I/M (B) IM (C) √(I/M) (D) √(IM) [1 marks]
  2. (a) Define simple harmonic motion. [1] (b) Derive an expression for the total mechanical energy of a particle executing simple harmonic motion. [3] (c) Show graphically how the kinetic energy, potential energy and total energy of the particle vary with displacement from its equilibrium position. [1] [5 marks]
  3. (a) What is the significance of the negative energy of the electron in an orbit? [1] (b) The diagram shows the lowest four discrete energy levels of an atom (n=1: −54.4 eV; n=2: −13.6 eV; n=3: −6.04 eV; n=4: ?). An electron in the n=4 state makes a transition to n=2, emitting a photon of wavelength 121.9 nm. (i) Calculate the energy level of n=4. [1] (ii) Calculate the momentum of the photon. [1] (c) The photon is then incident on a silver surface in a photoelectric experiment, and the surface emits an electron with maximum possible kinetic energy. If the work function of silver is 4.7 eV: (i)... [8 marks]
  4. The maximum velocity and maximum acceleration of a particle executing SHM are 4 m/s and 2 m/s² respectively. Its time period of oscillation is (A) π/2 sec (B) 2π sec (C) 2/π sec (D) 4π sec [1 marks]
  5. (a) What is meant by surface energy of a liquid? Write its relation with the surface tension of the liquid. [2] (b) An air bubble of radius 1 cm is rising at a steady rate of 5 mm/s through a liquid of density 0.8 g/cm³. Calculate the coefficient of viscosity of the liquid. (Neglect the density of air.) [3] [5 marks]
  6. (a) Two narrow slits are illuminated by a single monochromatic source of light. Name the pattern obtained on the screen and explain how these patterns are obtained. [1] (b) One of these slits is now completely covered. Name the pattern obtained on the screen. [1] (c) Write the difference between the patterns obtained in the above two cases on the basis of Huygens' principle. [1] (d) A monochromatic light of wavelength λ is incident normally on a narrow slit of width d and focused on a screen. Derive the condition for the first minimum of intensity on the screen in terms of wavelength λ and ang... [8 marks]
  7. A spherical ball is dropped into a long column of a viscous liquid. The speed (v) of the ball as a function of time (t) may be best represented by [velocity–time graphs (A), (B), (C), (D)]. [1 marks]
  8. (a) Draw a PV diagram of a petrol engine and explain its working based on the PV diagram. [3] (b) Why is Cp always greater than Cv? Explain. [2] [5 marks]
  9. (a) State Kirchhoff's laws for electrical circuits. [2] (b) The Wheatstone Bridge is a good engineering circuit design with several applications. (i) Draw the Wheatstone Bridge circuit diagram. [1] (ii) State the Wheatstone Bridge principle. [1] (iii) Use Kirchhoff's law to derive the balanced condition for the Wheatstone Bridge circuit. [1] (c) What is thermoelectric effect? Discuss the variation of thermo-emf with the temperature of the hot junction of a thermocouple. [3] OR (a) What is electrical resonance of a series LCR circuit? [1] (b) Calculate the resonant frequency of a series LCR cir... [8 marks]
  10. In which of the following processes of the gas is the work done the maximum? (A) Isothermal (B) Adiabatic (C) Isobaric (D) Isochoric [1 marks]
  11. (a) What is Doppler's effect? Calculate the apparent frequency when a source moves towards a stationary observer. [1+2] (b) Why are sound waves also called pressure waves? Explain. [2] [5 marks]
  12. When the door of a refrigerator is left open in a room, the temperature of the room (A) Increases (B) Decreases (C) Remains same (D) First increases, then decreases [1 marks]
  13. (a) State Lenz's law in electromagnetism. Does this law violate the principle of conservation of energy? Explain. [3] (b) In the figure, a magnet is moving towards one end of a solenoid connected to a sensitive galvanometer, inducing a current. Does the direction of the induced current change if the magnet is moved away from the solenoid? Explain. [2] [5 marks]
  14. The distance between two consecutive nodes in a standing wave is (A) λ (B) λ/2 (C) λ/4 (D) 2λ [1 marks]
  15. (a) Define one ampere of current in terms of the force between two parallel current-carrying conductors. [1] (b) How do you explain the contraction of the solenoidal coil while current is passed through it? [1] (c) A horizontal straight wire of mass 0.12 g and length 10 cm is placed perpendicular to a uniform horizontal magnetic field of flux density 0.6 T. If the resistance per unit length of the wire is 3.8 Ω m⁻¹, calculate the potential difference to be applied between the ends of the wire to make it just self-supporting. [3] OR (a) What do you mean by Seebeck effect? [1] (b) Explain the va... [5 marks]
  16. The critical angle of a certain medium is sin⁻¹(3/5). Then the polarizing angle of the medium will be (A) tan⁻¹(4/3) (B) tan⁻¹(3/4) (C) tan⁻¹(3/5) (D) tan⁻¹(5/3) [1 marks]
  17. (a) What is meant by specific charge of an electron? Its value is constant for cathode rays but not for positive rays — why? [2] (b) A beam of electrons is under the effect of a potential difference 1.36×10⁴ V applied across two parallel plates 4 cm apart and a magnetic field of 2×10⁻³ Wb/m² at right angles to each other. (i) Calculate the velocity of the electrons if the two fields produce no deflection in the beam. [1] (ii) What will be the radius of the orbit in which the beam moves if the electric field is made zero? [2] [5 marks]
  18. The value of the magnetizing field (H) when the magnetic flux density equals zero (B = 0) is called (A) Retentivity (B) Hysteresis (C) Coercivity (D) Curie's temperature [1 marks]
  19. (a) Define the terms half-life and decay constant of a radioactive substance. [2] (b) In a given sample, two radioisotopes A and B are initially present in the ratio 1:4. The half-lives of A and B are 100 years and 50 years respectively. Find the time after which the amounts of A and B become equal. [3] OR (a) What characteristic of a junction diode is used in rectification? [1] (b) Explain the working of a junction diode as a full-wave rectifier. [2] (c) The output of a two-input AND gate is fed to a NOT gate. Give its logic symbol and construct its truth table. [2] [5 marks]
  20. In our country, the supply of a.c. voltage is 220 V. The peak voltage is (A) 310 V (B) 110 V (C) 220 V (D) 350 V [1 marks]
  21. A long solenoid carrying a current produces a magnetic field B along its axis. If the current is doubled and the number of turns per cm is halved, then the new value of the magnetic field is (A) B (B) 2B (C) B/2 (D) 4B [1 marks]
  22. Which of the following earthquake waves is first recorded on the seismograph? (A) S-waves (B) P-waves (C) Love waves (D) Rayleigh waves [1 marks]