CBSE Class 12 Physics Viva Questions with Answers 2025

The CBSE Class 12 Physics viva is an essential part of the practical exams, offering students a chance to showcase their understanding of physics concepts and experiments. This evaluation tests their theoretical knowledge, practical application skills, and confidence in explaining procedures and results.

To excel in the viva, students should prepare thoroughly by reviewing experiment objectives, formulas, step-by-step methods, and key precautions. Familiarity with laboratory instruments and the reasoning behind their use is also crucial. Consistent practice with chapter-wise questions and previous year’s viva patterns ensures students are well-prepared to perform confidently and achieve high marks in this critical assessment.

CBSE Class 12 Physics Viva Introduction

The CBSE Class 12 Physics viva questions for 2025 are designed to test students’ grasp of theoretical and experimental physics concepts. These questions, aligned with the practical CBSE syllabus, focus on evaluating the understanding of principles, experimental methods, and result analysis. Preparing thoroughly with chapter-wise questions and previous year examples can help students confidently excel in their viva exams, showcasing their skills and knowledge effectively.

Also Check: CBSE Class 12 Biology Viva Questions with Answers 2025

CBSE Class 12 Physics Viva Questions with Answers PDF

The CBSE Class 12 Physics Viva Questions with answers PDF provides a detailed compilation of crucial viva questions along with their answers, helping students prepare thoroughly. This resource is designed to help students prepare efficiently, covering critical theoretical concepts, practical experiments, and important physics applications. Utilize this PDF to revise key topics, strengthen your understanding, and boost confidence ahead of the viva exam.

Download Available: CBSE CLASS 12 PHYSICS VIVA QUESTIONS WITH ANSWERS PDF 

CBSE Class 12 Physics Viva Questions and Answers 2025

General Viva Questions

1. What is the principle of Ohm’s Law?
   Answer: Ohm’s Law states that the current flowing through a conductor is directly proportional to the voltage across its ends, provided the temperature remains constant. $V = IR$.
2. Define the term 'electric potential.'
   Answer: Electric potential is the work done to move a unit positive charge from infinity to a point in an electric field without acceleration.
3. What are the SI units of resistivity?
   Answer: Resistivity is measured in ohm-meters (Ω⋅m) in the SI unit system.
4. Explain the significance of a galvanometer in experiments.
   Answer: A galvanometer detects and measures small currents in a circuit, often used to indicate the direction and magnitude of current.
5. State Kirchhoff’s Voltage Law (KVL).
   Answer: Kirchhoff's Voltage Law (KVL) asserts that the total sum of all the electrical potentials (voltages) around any closed loop in a circuit must equal zero.

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Experiment-Specific Questions

6. What is the function of a rheostat in a circuit?
   Answer: A rheostat is a device that allows the adjustment of resistance within a circuit, enabling control over the flow of current.
7. Why is a convex lens used to determine the focal length of a mirror?
   Answer: A convex lens focuses parallel rays at a point, helping determine the focal length of a mirror accurately.
8. How does the resistance of a conductor change if its length is doubled?
   Answer: The resistance of the conductor doubles, as resistance is directly proportional to the length.
9. Why is a prism used to study dispersion of light?
   Answer: A prism separates light into its component colors (spectrum) due to varying refractive indices for different wavelengths.
10. What is the significance of using a potentiometer in measuring EMF?
    Answer: A potentiometer provides a null point, ensuring more accurate and sensitive measurement of EMF compared to a voltmeter.

Wave and Optics Viva Questions

11. Define the term 'diffraction.'
    Answer: Diffraction is the bending of light around the edges of an obstacle or aperture, producing a pattern of bright and dark fringes.
12. What is the difference between interference and diffraction?
    Answer: Interference is the superposition of waves from two coherent sources, while diffraction occurs due to bending of waves around obstacles.
13. Why do soap bubbles exhibit vibrant colors?
    Answer: Soap bubbles show colors due to thin-film interference of light reflected from the bubble's surfaces.
14. What is Brewster’s angle?
    Answer: Brewster’s angle is the angle of incidence at which light is perfectly polarized upon reflection.
15. Explain the working of a diffraction grating.
    Answer: A diffraction grating disperses light into its component wavelengths due to constructive and destructive interference from closely spaced lines.

Modern Physics Viva Questions

16. What is the photoelectric effect?
    Answer: The photoelectric effect is the emission of electrons from a metal surface when it is exposed to light of sufficient energy.
17. Define work function in photoelectric emission.
    Answer: The work function is the minimum energy required to eject an electron from a metal surface.
18. What is the significance of Planck’s constant?
    Answer: Planck’s constant relates the energy of a photon to its frequency, $E = h \nu$.
19. What are isotopes?
    Answer: Isotopes are variations of the same element that have the same number of protons but differ in the number of neutrons they contain.
20. Explain the term ‘half-life.’
    Answer: Half-life is the time taken for half of a radioactive substance to decay.

Practical Application Viva Questions

1. How does an increase in temperature influence the resistance of a conductor?
   Answer: Resistance increases with temperature for conductors due to increased collisions among charge carriers.
2. Why is a meter bridge more accurate for resistance measurement?
   Answer: A meter bridge uses the null deflection method, minimizing errors in resistance measurement.
3. What is the function of a diode in a circuit that converts AC to DC?
   Answer: A diode permits current to flow in only one direction, enabling the conversion of alternating current (AC) into direct current (DC) in a rectifier circuit.
4. What happens to the current in a circuit if the voltage is tripled?
   Answer: The current triples, as $I \propto V$, provided resistance remains constant.
5. What is the basic principle of a transformer?
   Answer: A transformer operates based on electromagnetic induction to either increase or decrease the AC voltage.

Magnetism and Electromagnetic Induction Viva Questions

26. State Faraday’s Law of Electromagnetic Induction.
    Answer: Faraday’s Law states that an EMF is induced in a conductor when the magnetic flux through it changes.
27. What distinguishes diamagnetic materials from paramagnetic materials?
    Answer: Diamagnetic materials repel magnetic fields, while paramagnetic materials are weakly attracted to magnetic fields.
28. What is the function of an inductor in a circuit?
    Answer: An inductor stores energy in the form of a magnetic field and opposes changes in current.
29. Why do we use soft iron in electromagnets?
    Answer: Soft iron enhances the magnetic field strength and can be easily magnetized and demagnetized.
30. What is the principle of a moving coil galvanometer?
    Answer: It works on the principle that a current-carrying coil in a magnetic field experiences a torque proportional to the current.

Advantages of Solving CBSE Class 12 Physics Viva Questions

• Enhances Conceptual Understanding: Practicing viva questions helps students deeply understand fundamental physics concepts and their applications.
• Boosts Confidence: Regular practice prepares students to confidently answer challenging questions during exams.
• Improves Communication Skills: Explaining answers verbally improves clarity and articulation, which is essential for viva exams.
• Reinforces Practical Knowledge: Solving viva questions ensures a thorough understanding of experiments, apparatus, and procedures.
• Prepares for Unexpected Questions: Familiarity with diverse questions helps students tackle unpredictable queries during the viva.
• Strengthens Problem-Solving Abilities: Working on complex questions enhances analytical and critical thinking skills.
• Highlights Key Areas for Revision: Solving questions identifies weak topics that need more focus during preparation.
• Facilitates Time Management: Practice helps students answer concisely and efficiently within the limited time of a viva exam.
• Links Theory with Practical Applications: Understanding the theoretical basis of experiments strengthens academic performance.
• Reduces Exam Stress: Confidence gained from practice lowers anxiety and improves overall performance in viva assessments.