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Punjab Board Class 12 Physics Question Paper Held on 4 March 2025 ANSWER KEY

Punjab Board Physics Answer Key 2025 (March 4th) | pb.jobsoftoday.in

Punjab Board Physics Exam 2025: Answer Key Released (March 4th)

The highly anticipated Punjab School Education Board (PSEB) Class 12th Physics examination, held on March 4th, 2025, has concluded, and students are eagerly seeking the answer key to assess their performance. We understand the anxiety and curiosity that follows any major examination, and we're here to provide you with the latest updates.

The Physics exam, a crucial component of the science stream, tested students on various concepts and applications. With the release of the official or unofficial answer key, students can now cross-reference their answers and get an estimate of their scores.

Why is the Answer Key Important?

  • Self-Assessment: The answer key allows students to evaluate their performance and identify areas where they might have made mistakes.
  • Reduced Anxiety: Knowing the correct answers can alleviate the post-exam stress and provide clarity.
  • Preparation for Future Exams: Analyzing the answer key helps students understand the exam pattern and the types of questions asked, aiding in future preparation.

Where to Find the Answer Key:

  • Official PSEB Website: Keep an eye on the official Punjab School Education Board website (pseb.ac.in) for official releases.
  • Educational Portals: Many educational websites and platforms will publish unofficial answer keys shortly after the exam.
  • Your Website: We will try to provide the most updated answer key as soon as we can. Please keep checking pb.jobsoftoday.in for updates.

Important Notes:

  • Unofficial answer keys may have variations, so it's best to wait for the official release for accurate results.
  • Focus on learning from your mistakes rather than solely focusing on the score.

We wish all the students the very best for their results. Stay tuned to pb.jobsoftoday.in for more updates on PSEB results, answer keys, and other educational resources.

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Question Paper

Question Paper

(English Version)

Note:

  1. You must write the subject-code/paper-code 052 in the box provided on the title page of your answer-book.
  2. Make sure that the answer-book contains 32 pages (including title page) and are properly serialled as soon as you receive it.
  3. Question/s attempted after leaving blank page/s in the answer-book would not be evaluated.
  4. Log tables may be asked for if needed.
  5. Use of Un-programmable calculator is allowed.
  6. Q. Nos. 1 has 20 questions and each question carry one mark each.
  7. Q. Nos. 2 to 8 carry two marks each.
  8. Q. Nos. 9 to 15 carry three marks each.
  9. Q. Nos. 16 to 18 carry five marks each.
  10. Punjabi and Hindi Versions of questions are true translation of English Version. So in the case of any confusion consider English Version to be Correct.

One mark questions: 20x1=20

  1. (i) What is the peak value of AC 220 Volt?

    1. 220 V
    2. 311 V
    3. 320 V
    4. 440 V

    Answer: b. 311 V

  2. (ii) Which has the longest wavelength?

    1. X-rays
    2. Micro waves
    3. Infrared rays
    4. Radio waves

    Answer: d. Radio waves

  3. (iii) The image of real object as seen through convex mirror is:

    1. real
    2. virtual
    3. sometimes real, sometimes virtual
    4. none of these

    Answer: b. virtual

  4. (iv) Hugen's wave theory allows us to know about:

    1. the wavelength of the wave.
    2. the velocity of the wave.
    3. the amplitude of the wave.
    4. the propagation of wavefronts.

    Answer: d. the propagation of wavefronts.

  5. (v) Velocity of light is maximum in:

    1. vacuum.
    2. water.
    3. diamond.
    4. glass.

    Answer: a. vacuum.

  6. (vi) The conversion of light energy into electrical energy is achieved in a:

    1. Coolidge tube.
    2. Thermocouple.
    3. Photo cell.
    4. Cloud chamber.

    Answer: c. Photo cell.

  7. (vii) The maximum kinetic energy of the photoelectrons depends only on:

    1. incident angle.
    2. frequency.
    3. pressure.
    4. potential.

    Answer: b. frequency.

  8. (viii) In the Bohr model of hydrogen atom, the lowest orbit corresponds to:

    1. maximum energy.
    2. minimum energy.
    3. zero energy.
    4. infinite energy.

    Answer: b. minimum energy.

  9. (ix) On doping the conductivity of semi-conductor:

    1. increases.
    2. remains same.
    3. decreases.
    4. none of these.

    Answer: a. increases.

  10. (x) Applying forward bias in p-n junction, the potential barrier:

    1. decreases.
    2. increases.
    3. remains unchanged.
    4. becomes zero.

    Answer: a. decreases.

  11. (xi) When the distance between the charges is halved, the force between the charges become:

    1. half
    2. twice
    3. four times
    4. none of these

    Answer: c. four times.

  12. (xii) If a dielectric is kept between two plates of capacitor, its capacitance:

    1. increases
    2. decreases
    3. First increases then decreases
    4. none of these

    Answer: a. increases.

  13. (xiii) Wheatstone bridge is used to measure:

    1. e.m.f.
    2. potential
    3. resistance
    4. current

    Answer: c. resistance.

  14. (xiv) The ultimate individual unit of magnetism in any magnet is:

    1. north pole
    2. south pole
    3. magnetic dipole
    4. quadrupole

    Answer: c. magnetic dipole.

  15. (xv) The laws of electromagnetic induction have been used in the construction of:

    1. voltmeter
    2. ammeter
    3. electric motor
    4. generator

    Answer: d. generator.

True/False

  1. (xvi) Diffraction of light is the phenomenon of bending of light around the corners of an aperture in its path. (T/F)

    Answer: True

  2. (xvii) The strength of bar magnet is maximum at its center. (T/F)

    Answer: False

  3. (xviii) Semi-conductor is a device that obeys Ohm's law. (T/F)

    Answer: False

  4. (xix) The density of nuclear matter is independent of the size of the nucleus. (T/F)

    Answer: True

  5. (xx) The size of the mirror does not affect the nature of image. (T/F)

    Answer: False

Two marks questions: 7x2=14

  1. Define threshold wavelength and frequency.

    OR

    Calculate the de-Broglie wavelength for electrons moving with speed of 105 m/s.

  2. Write an expression for mass defect.

  3. Why can't two equipotential surfaces intersect each other?

    OR

    Calculate the Coulomb's force between proton and electron separated by distance of 0.8 x 10-15 m.

  4. What is resistance? Define SI unit of resistance.

    OR

    Calculate the resistivity of material of conductor of length 3 m, area of cross section 0.2 mm2 having a resistance of 2 Ω.

  5. Derive an expression for magnetic force. How the direction of magnetic force is determined?

  6. What are the factors which reduce the efficiency of a transformer?

  7. What is displacement current?

Three mark questions: 7x3=21

  1. Find the focal length of combination of two thin lenses in contact.

    OR

    Two lenses, one diverging of power 2D and the other converging of power 6D are combined together. Calculate the focal length and power of combination.

  2. Write down at least three properties of nuclear force.

  3. With the help of circuit diagram explain V-I characteristics of p-n junction in reverse biasing.

  4. Derive an expression for potential energy of a charged capacitor.

  5. Find the total resistance of a circuit, in which three resistances are connected in series.

  • Explain Biot Savart's law for a small current carrying conductor.

    OR

    A proton enters into a magnetic field of intensity 5 x 10-2 Tesla with velocity of 105 m/s at an angle of 30° with the field. Calculate the magnitude of force acting on proton due to this field.

  • Define coefficient of self-induction and find an expression for it for a solenoid.

    OR

    A wire is cut across a flux of 0.2 x 10-2 weber in 0.12 seconds. What is the e.m.f. induced in the wire?

    • Five mark questions: 5x1=5

    1. Read the following paragraph and answer the questions given below.

      Ferromagnetic substances are those which get strongly magnetized when placed in an external magnetic field. They have strong tendency to move from a region of weak magnetic field to strong magnetic field, that is, they get strongly attracted to a magnet. The individual atoms (or ions or molecules) in a ferromagnetic material possess a dipole moment as in a paramagnetic material. However, they interact with one another in such a way that these spontaneously align themselves in a common direction over a macroscopic volume called domain. Each domain has a net magnetization. Typical domain size is 1 mm and the domain contains about 1011 atoms. In the first instant the magnetization varies randomly from domain to domain and there is no bulk magnetization. When we apply an external magnetic field Bo the domains orient themselves in the direction of Bo and simultaneously that domain oriented in the direction of Bo grows in size. We may wonder as to what happens when the external field is removed, in some ferromagnetic materials the magnetization persists. Such materials are called hard magnetic materials of hard magnets. Alnico, an alloy of iron, aluminium, nickel, cobalt and copper is one such material. There is a class of magnetic materials in which the magnetization disappears on removal of the external field. Soft iron is one such material. Such materials are called soft ferromagnetic materials. There are number of elements which are ferromagnetic. Iron, cobalt, Nickel, gadolinium etc. The ferromagnetic property depends on temperature. At high enough temperature a ferromagnet becomes a paramagnet. That domain structure disintegrates with temperature. This disappearance of magnetization with the temperature is gradual.

      Questions:

      1. What will be the effect of temperature on ferromagnets?
      2. What are ferromagnetic substances?
      3. What is the domain size of ferromagnetic substances?
      4. How many numbers of atoms are there in one domain?
      5. Write any three examples of ferromagnets.

    Answers:

    1. At high enough temperature a ferromagnet becomes a paramagnet. The domain structure disintegrates with temperature.
    2. Ferromagnetic substances are those which get strongly magnetized when placed in an external magnetic field.
    3. The typical domain size is 1 mm.
    4. One domain contains about 1011 atoms.
    5. Iron, cobalt, nickel.

    Five marks questions:

    1. Using Gauss theorem derive an expression for electric field intensity due to uniformly charged hollow sphere (shell) at a point outside the shell and at a point inside the shell.

      OR

      Derive an expression for capacitance of parallel plate capacitor with a dielectric slab between the plates.

    2. Write the assumptions, sign conventions and then derive the mirror formula for concave mirror.

      OR

      What is diffraction of light? Explain diffraction at single slit and deduce expression for width of its central maxima.

    PUNJAB BOARD PHYSICS QUESTION PAPER 2025 Download here

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