Class: 12 Physics Sample Paper 1

Class: 12 Physics Sample Paper 1

Gyanpoints

learn and practice with Gyanpoints

Board EXAMINATION 2025-2026

Class: 12 | Subject: Chemistry (043) | Set: 2

Max Marks: 70 | Time: 3 Hours

Date: 13/12/2025

General Instructions:

  • This question paper contains 33 questions. All sections are compulsory.
  • Section A: 16 questions (12 MCQs and 4 Assertion-Reasoning) of 1 mark each.
  • Section B: 5 questions of 2 marks each.
  • Section C: 7 questions of 3 marks each.
  • Section D: 2 case study-based questions of 4 marks each.
  • Section E: 3 long answer questions of 5 marks each.
  • There is no overall choice. However, internal choices have been provided in some questions.
  • Use of calculators is not allowed.

Physical Constants:

  • (i) \( c = 3 \times 10^{8} \, m/s \)
  • (ii) \( m_{e} = 9.1 \times 10^{-31} \, kg \)
  • (iii) \( e = 1.6 \times 10^{-19} \, C \)
  • (iv) \( \mu_{0} = 4\pi \times 10^{-7} \, TmA^{-1} \)
  • (v) \( h = 6.63 \times 10^{-34} \, Js \)
  • (vi) \( \epsilon_{0} = 8.854 \times 10^{-12} \, C^{2}N^{-1}m^{-2} \)
  • (vii) Bohr radius \( = 0.53 \times 10^{-10} \, m \)

SECTION A (1 Mark Each)

1. Two identical solenoids X and Y, one is wound over a material whose \( \chi \) is low positive and another one is wound over a material whose \( \chi \) is low negative respectively. A graph is plotted between current in the solenoid Vs magnetic flux. The solenoid in which the magnetic material of low positive is wound, is:

  1. X since self inductance is high
  2. Y since self inductance is low
  3. X since self inductance is low
  4. Y since self inductance is high

2. A plano-concave lens is made of a material of refractive index \( \mu = 1.5 \). The radius of curvature of curved surface of the lens is 20 cm. If its plane surface is silvered, the focal length of the silvered lens will be:

  1. -10 cm
  2. -20 cm
  3. -40 cm
  4. -80 cm

3. The linear momentum of alpha particle which is accelerated by a potential of V is:

  1. \( \sqrt{2(2m)eV} \)
  2. \( \sqrt{2(m)eV} \)
  3. \( 4\sqrt{(m)eV} \)
  4. \( \sqrt{2(m)(2e)V} \)

4. Which one of the following is correct statement regarding the Rutherford alpha scattering experiment?

  1. As KE of alpha particle increases, distance of closest approach increases.
  2. When impact parameter is zero, the distance of closest approach approximately gives the size of the nucleus.
  3. When impact parameter increases, for given KE of alpha particle, angle of scattering of alpha particle increases.
  4. When KE increases, for given impact parameter, then angle of scattering increases.

5. Which transition corresponding to the absorption of energy 3 eV using energy level diagram?

  1. D
  2. A
  3. B
  4. C

6. In a p-n junction diode, when it is FB (Forward Biased), kinetic energy of the electron is:

  1. due to barrier potential only
  2. due to applied voltage only
  3. due to difference of applied voltage and barrier potential
  4. due to addition of applied voltage and barrier potential

7. Suppose a pure Si crystal has \( 5 \times 10^{28} /m^{3} \). It is doped by 50 ppm concentration of Arsenic. The number density of holes is \( [n_i = 1.5 \times 10^{16} /m^{3}] \):

  1. \( 2.50 \times 10^{8} /m^{3} \)
  2. \( 2.250 \times 10^{11} /m^{3} \)
  3. \( 4.50 \times 10^{9} /m^{3} \)
  4. \( 2.50 \times 10^{18} /m^{3} \)

8. A charged particle q is placed at the centre O of (ABCDEFGH) of length L. Another similar charge q is placed at a distance L from O. Then, the electric flux through ABCD is:

  1. \( q/\epsilon_{0} \)
  2. \( q/6\epsilon_{0} \)
  3. Zero
  4. \( 2q/6\epsilon_{0} \)

9. The physical quantity \( X = (E/(R+r))^{2} \times R \) having usual meaning. The SI unit of X is:

  1. \( V^{2}-\Omega \)
  2. \( V^{2}-\Omega^{2} \)
  3. Watt-Second
  4. \( J/S \)

10. Three identical cells, each of e.m.f. 2 V and unknown internal resistance are connected in parallel. This combination is connected to a 9 ohm resistor. If the terminal voltage across the cell is 1.5 volt, the internal resistance of each cell is:

  1. 3 \( \Omega \)
  2. 9 \( \Omega \)
  3. 12 \( \Omega \)
  4. 4.5 \( \Omega \)

11. A network of four capacitors \( C_{1}=2C, C_{2}=6C, C_{3}=3C, C_{4}=4C \) are connected as shown in figure. The ratio of the charges on \( C_{2} \) to \( C_{4} \) is:

  1. 1:1
  2. 1:8
  3. 1:4
  4. 1:6

12. A circular loop of radius R carrying current I produces magnetic field B at its centre. The magnetic field at a point P at a distance X from the centre of the same current loop along its axis is \( 1/8 \)th of B. The value of X is:

  1. 2R
  2. 3R
  3. \( \sqrt{8} R \)
  4. \( \sqrt{3} R \)

Directions for Questions 13 to 16: Two statements are given - one labelled Assertion (A) and other labelled Reason (R). Select the correct answer from the codes (a), (b), (c), and (d) as given below:

  • (a) If both Assertion and Reason are true and Reason is correct explanation of Assertion.
  • (b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
  • (c) If Assertion is true but Reason is false.
  • (d) If both Assertion and Reason are false.

13. Assertion: When a ray of light travels from one medium to another medium, the frequency of light changes but wavelength of light remains the same.
Reason: Wavelength of light is independent of medium it wont change.

14. Assertion: As the mass number of the nucleus increases, the radius of the nuclei also increases.
Reason: The volume of the nucleus is directly proportional to \( A^{1/3} \) where A is the mass number.

15. Assertion: Two bulbs A and B each power P are connected in series to a source. When bulb A is replaced with another bulb of power 2P, the brightness of bulb B decreases.
Reason: Since current in the circuit decreases, due to increase in the resistance of the circuit, brightness of the bulb B decreases.

16. Assertion: When two like charges are separated by a distance d, the zero electric field point can be obtained outside as well as in between the two charges.
Reason: Electric field at a point is the algebraic sum of electric field due to two point charges.

SECTION B (2 Marks Each)

17. (i) In the wave picture of light, intensity of light is determined by the square of the amplitude of the wave. What determines the intensity of light in the photon picture of light?

(ii) If the distance between three consecutive bright fringes in YDSE is 4mm, how many bright fringes will occupy the distance of 8cm?

18. An electron is revolving around the nucleus in a stable orbit whose circumference is 5.325nm. Find the principle quantum number of the orbit and draw suitable diagram of standing waves fit in that orbit.

19. Draw energy band diagram of extrinsic semiconductor in which boron is doped with intrinsic semiconductor \( (T>0 K) \). In this crystal, how neutrality is maintained though the majority carriers dominate minority carriers?

OR

Draw output waveform across load resistor \( R_L \) and across diode for the given input waveform as shown.

20. (i) A infinitely long charged plane sheet of charge density \( 5 \times 10^{-16} C/m^{2} \). A dipole of dipole moment \( 2 \times 10^{-7} C-m \) is placed as shown in figure. Then the dipole is rotated by 30° in clockwise and further it is rotated by 60°. Find the potential energy in all the three positions of dipole.

OR

(ii) A pendulum of mass m carrying charge Q is suspended between two infinitely long charged plane sheets as shown in figure. The pendulum makes an angle of \( \theta \) with vertical at equilibrium. Obtain an expression for \( \tan\theta \) in terms of \( m, \theta, q \).

21. Show that in interference there is redistribution of light wave energy and there is no loss of energy. Why cannot we observe diffraction when light is passing through grilled window? Explain.

SECTION C (3 Marks Each)

22. (i) Show that during the charging of a parallel plate capacitor, the rate of change of charge on each plate equals \( \epsilon_{0} \) times the rate of change of electric flux (\( \Phi_E \)) linked with it. What is the name given to the term \( \epsilon_{0} [d\Phi_E/dt] \)? A capacitor is connected to dc source and when the capacitor is fully charged, what is the value of conduction current?

(ii) A special device like Klystron valve, is used for the production of EMW. Name the EM waves and also write one application of it.

23. A small telescope has an objective lens of focal length 140cm and an eyepiece of focal length 5.0cm.
a) What is the magnifying power of the telescope for viewing distant objects when the final image is formed at the least distance of distinct vision (25cm)?
b) If this telescope is used to view a 100 m tall tower 3 km away, what is the height of the image of the tower formed by the objective lens?
c) What is the height of the final image of the tower if it is formed at 25cm?

24. A graph is plotted between \( V_{max}^{2} \) Vs \( 1/\lambda \) graph in photo electric emission for a metal surface P. The intercept on X axis gives the value of \( 1.6 \times 10^{6} /m \) and on Y axis gives \( 7 \times 10^{11} \) in SI unit. Calculate the value of work function in eV. If a light of energy 4eV is incident on the metal surface P, calculate the stopping potential.

25. Plot a graph between the binding energy per nucleon \( E_{bn} \) versus the mass number A for a large number of nuclei. Explain the importance of the graph in explaining nuclear fission and fusion process. What is the reason for the constancy of the binding energy per nucleon between \( 30 < A < 170 \)?

26. (i) Four charges each charge q are placed at the corners of the square of side 'a'. Another charge Q is placed at the centre of the square. Find the value of Q in terms of q so that the system of charges are in equilibrium.

(ii) A spherical shell of radius 20cm carries a charge of 10µC. What is the workdone in moving a charge of 2µC diametrically opposite points along the surface of the sphere?

OR

Three concentric spherical shells A, B and C of radius a, b, c having surface charge density \( +\sigma, -\sigma, +\sigma \) respectively \( [a

27. (i) Draw magnetic field lines around a magnetic substance which is placed in external magnetic field whose relative magnetic permeability is 0.5.
(ii) Does the magnetic field lines get repelled or attracted due to this magnetic material? Explain.
(iii) Plot a graph between intensity of magnetisation of this magnetic material Vs magnetising field.

28. A slider of length l is moving with velocity v normal to MF of strength B acting outward. Obtain an expression for emf induced across the slider only by using Lorentz force and mark the polarity of emf induced in the slider. Are you doing work against any force when a slider is moved in magnetic field normally? Explain.

SECTION D (Case Study - 4 Marks Each)

29. Case Study: Motion of Charged Particle in Magnetic Field

A proton is moving with velocity \( 8 \times 10^{6} m/s \) entering a uniform magnetic field of strength 0.04T such that the velocity vector makes an angle of 30° with the field. The ratio of charge to mass of proton is \( 10^{8} C/kg \).

(i) The radius of the path described by the proton is:

  1. 1 m
  2. 1 cm
  3. 0.5 m
  4. 2 m

(ii) The path described by the proton due to horizontal component of velocity in uniform MF is:

  1. Helix
  2. Straight
  3. Circular
  4. All the above

(iii) The kinetic energy of the proton in MeV is:

  1. 0.16
  2. 22.7
  3. 0.66
  4. 0.33

(iv) The frequency of the rotation of proton is:

  1. \( 0.64 \times 10^{6} Hz \)
  2. \( 1.2 \times 10^{6} Hz \)
  3. \( 0.32 \times 10^{6} Hz \)
  4. \( 2.4 \times 10^{6} Hz \)

OR

(v) The correct expression for the pitch of the proton is:

  1. \( v \cos\theta \times (Bq/2\pi m) \)
  2. \( v \cos\theta \times (2\pi m/Bq) \)
  3. \( v \sin\theta \times (Bq/2\pi m) \)
  4. \( v \sin\theta \times (2\pi m/Bq) \)

30. Case Study: p-n Junction Diode

A p-n junction is the basic building block of many semiconductor devices like diodes, transistor, etc. Consider a thin p-type silicon (p-Si) semiconductor wafer. By adding precisely a small quantity of pentavalent impurity, part of the p-Si wafer can be converted into n-Si. There are several processes by which a semiconductor can be formed. The wafer now contains p-region and n-region and a metallurgical junction between p-, and n- region.

(i) In an unbiased p-n junction, holes diffuse from the p-region to n-region because:

  1. free electrons in the n-region attract them.
  2. they move across the junction by the potential difference.
  3. hole concentration in p-region is more as compared to n-region.
  4. All the above.

(ii) During the formation of the diode, which one of the following is not correct statement?

  1. Due to diffusion of electrons and holes, a depletion region is formed.
  2. Due to junction field, electron from P side drifts towards the n side.
  3. The thickness of the depletion region is in the order of \( 1/10 \) th of micrometer.
  4. In a unbiased p-n junction diode, under equilibrium, there is net drift current since number density of electron is greater than number density of hole.

(iii) Figure a represents of barrier potential of diode. Which one of the statement represents correctly?

  1. (1) without battery, (2) Low battery voltage, and (3) High voltage battery, in reverse biasing.
  2. (1) without battery, (2) high battery voltage, and (3) low voltage battery, in forward biasing.
  3. (1) without battery, (2) Low battery voltage, and (3) High voltage battery, in forward biasing.
  4. (1) without battery, (2) high battery voltage, and (3) low voltage battery, in reverse biasing.

(iv) Which one of the following will not take place in forward biasing of diode?

  1. Thickness of the depletion layer decreases.
  2. Minority carrier injection takes place.
  3. The current is due to drift of electron from p side to n side and holes from n side to p side.
  4. In diode, n side of the diode is more negative than p side.

OR

(v) The effective resistance of the circuit containing resistors and ideal diodes during positive and negative half cycle of signal of the circuit respectively is:

  1. R, 3R
  2. 3R/4, 3R/4
  3. 5R/3, 3R/4
  4. 2R/3, 4R/3

SECTION E (Long Answer - 5 Marks Each)

31. (i) A series L-C-R circuit is connected to an AC source. Using the phasor diagram, derive the expression for impedance of the circuit. Using the same phasor diagram, obtain an expression for the average power consumed by this circuit.

(ii) Calculate the current drawn by the primary of a transformer which step-downs 200 V to 20 V to operate a device of resistance 20 \( \Omega \). Assuming the efficiency the transformer to be 80%.

OR

(iii) An ideal capacitor is connected to ac source \( E = E_{0} \cos(\omega t) \). Obtain an expression for the capacitive reactance and phase relation between voltage and current and plot a graph to show the instantaneous value of voltage and current in this circuit with time.

(iv) An inductor of 5 H, capacitor of 20µF and resistor of 40 ohm are connected in series to an ac source of \( E = 200\sqrt{2} \sin(\omega t) \). It is found that voltage across resistor and supply voltage are same, calculate the value of current and \( \omega \) of this circuit.

32. (i) Derive mirror formula for a curved mirror in which virtual enlarged image is obtained.

(ii) Two lenses, one is convex lens of power 5D and another one is concave lens of power 6.25D are placed co-axially. An object is placed infront of the convex lens at a distance of 30cm from the convex lens. The distance between the two lenses is 48cm. Find the final image distance from the concave lens, what is the nature of final image and calculate total magnification.

OR

(iii) Draw a neat labeled ray diagram of prism. Obtain relation between a) angle of refraction of two surfaces and refracting angle of prism and b) angle of deviation, angle of incidence, angle of emergence with refracting angle of prism. Plot a graph between angle of deviation with variation of angle of incidence.

(iv) A convex lens of focal length 20cm in air (Refractive index of lens \( n=1.5 \)). It is dipped completely in liquid of refractive index \( n_1 \), the focal length of lens now becomes 20cm and behaves as an divergent. Find the value of \( n_1 \). What is the value of refractive index of \( n_1 \) so that power of the convex lens becomes zero?

33. (i) Define drift velocity of electron in a metallic conductor and relaxation time and obtain relation between drift velocity and relaxation time. Plot a graph between drift velocity of electron with variation of temperature.

(ii) In the Wheatstone network, find the value of R if the current drawn from the battery is 2A.

OR

(iii) Define resistivity of material of substance. Obtain relation relating resistivity and relaxation time.

(iv) Calculate the current drawn from the battery.

Tags:

Comments

Post a Comment