Viva Questions for Class 12 Physics

Viva Questions for Class 12 Physics
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Mastering Class 12 Physics Viva Questions for CBSE Board Exams: Preparing for the Class 12 Physics practical exam requires thorough understanding and practice, especially for the viva questions. The Physics Practical Viva Class 12 often focuses on core concepts from the Physics Lab Manual and the practical experiments conducted during the academic year. Students must prepare key Viva Topics, such as Ohm’s law, electromagnetic induction, ray optics and Newton’s laws of motion, to tackle the Common Physics Viva Questions effectively. The CBSE Class 12 Practical Exam Guide recommends focusing on frequently asked questions and practicing detailed answers. Solid preparation not only boosts confidence but also ensures better performance in the Physics Viva for Board Exams.

Tips for Excelling in Class 12 Physics Practical Viva

The Class 12 Physics Viva with Answers plays a vital role in scoring well in the CBSE board practical exams. To ace it, students should focus on revising their Physics Practical Viva Class 12 thoroughly, as questions often test their understanding of experimental principles and theoretical concepts. Utilize resources like the CBSE Class 12 Physics Viva Guide and practice with peers to simulate real exam scenarios. Prepare answers for common questions like experimental setups, sources of error, and related theoretical principles. Additionally, downloading resources like the Physics Viva Questions PDF can be helpful. Proper preparation ensures that students face their Viva Voice Class 12 Physics with confidence and clarity.

The Class 12th Board Examination structure allocates 30 marks to practical, out of which a significant portion is attributed to the viva voice. These marks are divided into practical experiments, the practical file, project work and a separate viva assessment, which carries 6 marks. This part of the examination gives you a great opportunity to secure marks by demonstrating clarity in understanding and preparation.

Viva Questions for Class 12 Physics Exam

Welcome to the ultimate guide for excelling in your Class 12th Physics viva exams! The viva voice is an essential component of your practical examination, designed to test not only your knowledge of theoretical concepts but also your ability to connect them with real-world applications. Unlike the written exam, where answers are penned down, the viva evaluates your ability to articulate scientific ideas confidently and clearly in a verbal format.

This guide is specifically curated to help you prepare comprehensively. It focuses on important chapters such as Electrostatics, Magnetic Effects of Current, Electromagnetic Waves, Optics and Modern Physics, which often dominate viva questions. In addition, it elaborates on core experimental techniques, including circuit-based experiments and optical bench setups, which are commonly discussed.

Furthermore, the guide includes potential viva questions, concise explanations of key concepts, and tips to impress examiners with your scientific reasoning. Whether it’s defining Coulomb’s law, explaining the working of a potentiometer, or discussing the role of a dielectric in a capacitor, we’ve got you covered.
Dive into this guide, prepare thoroughly, and approach your viva with confidence to secure full marks and ace your Physics practical exams!

Class 12 Physics Practical Examination (CBSE)

The Class 12 Physics exam under the CBSE system is designed to evaluate both theoretical knowledge and practical skills. The examination is divided into two components: the Theory Examination and the Practical Examination. Below is the detailed marks distribution:
Theory Examination (70 Marks)
Electrostatics and Current Electricity (Unit I to III): 23 Marks
Magnetic Effects of Current and Magnetism (Unit IV to VI): 19 Marks
Electromagnetic Waves, Optics, and Modern Physics (Unit VII to X): 28 Marks
This structure ensures that key concepts across various domains, such as electricity, magnetism, optics, and modern physics, are thoroughly tested. The theory exam emphasizes critical thinking, conceptual clarity, and problem-solving abilities to assess your depth of understanding.
Practical Examination (30 Marks)
Viva Voice and Experiments: A significant portion of marks is awarded for viva voice and the performance in practical experiments.
Practical File/Project: 4 Marks
Class Record and Viva Based on Practical Conducted: 6 Marks
This breakdown ensures that students are assessed not only on their understanding of theoretical concepts but also on their practical knowledge and the ability to perform experiments. The practical exams focus on skills like measurement, observation, and analytical thinking, which are essential for mastering the subject.

Key Focus Areas for Preparation:
Theory Exam: Focus on understanding the core concepts, formulas, and applications. Practice numerical and derivations.
Practical Exam: Be well-prepared with the experiments, have a clear understanding of their principles and practice explaining them during the viva.
This exam structure emphasizes conceptual understanding, laboratory skills, and the ability to apply knowledge in both theoretical and practical settings.

1. Electrostatics

Key Topics to Focus: Coulomb’s law, Electric field and potential, Gauss’s theorem and its applications, Capacitors and energy stored in capacitors.
Important Viva Questions:

    1. State Coulomb’s law.
    2. What is an electric dipole? Define its dipole moment.
    3. Explain the principle of a capacitor.
    4. What is the significance of Gauss’s theorem?
    5. What are the properties of electric field lines?
    6. How does the potential vary with distance for a charge?

Key Points to Discuss in Viva:

    • Nature of Force: If q1 and q2 have the same sign (both positive or negative), the force is repulsive. If q1 and q2 have opposite signs, the force is attractive.
    • Vector Form of Coulomb’s Law: The force also has a directional component. If r is the vector joining the charges: F = k(q1q2/r³)r This vector form shows that the force acts along the line joining the charges.
    • Superposition Principle: When more than two charges are present, the net force on a charge is the vector sum of the forces due to other individual charges.
    • Properties of Electric Field: Electric field lines start from positive charges and end on negative charges. The density of field lines indicates the strength of the field. No two electric field lines can intersect. In a uniform electric field, field lines are parallel and equally spaced.
    • Key Relationships Between Electric Field and Potential: Electric field is a vector quantity, while electric potential is a scalar quantity. Electric field indicates the strength and direction of force, whereas electric potential measures the energy per unit charge. Potential decreases in the direction of the electric field
    • Capacitor Definition: A capacitor is a two-terminal electrical device used to store electrical energy in the form of an electrostatic field. Working Principle: When a voltage is applied across the terminals of a capacitor, it stores charge. The amount of charge stored is directly proportional to the applied voltage. Q= C.V where, Q = Charge stored (in Coulombs). C = Capacitance (in Farads). V = Voltage applied (in Volts).
    • Energy Stored in a Capacitor Expression for Energy Stored: The energy stored in a capacitor is given by: U = 1/2CV² where: U = Energy stored (in Joules) C = Capacitance (in Farads) V = Voltage applied (in Volts) Alternate Forms: U = 1/2QV = Q²/2C (Use the relation Q = C⋅VQ = C\cV Q = C⋅V to derive these.) Explanation: The work done in charging a capacitor is stored as potential energy in the electrostatic field between its plates.

2. Current Electricity

Key Topics to Focus: Ohm’s law and resistance, Kirchhoff’s laws and their applications, Wheatstone bridge and its principle, Potentiometer.
Important Viva Questions:

    1. Define resistivity and conductivity.
    2. What is the principle of a potentiometer?
    3. State and explain Kirchhoff’s laws.
    4. How can you determine the internal resistance of a cell?

Key Points to Discuss in Viva:
In a viva, when discussing Ohm’s Law, you should explain that it states the relationship between voltage (V), current (I), and resistance (R) in a conductor, expressed as V = IR. It shows that the current through a conductor is directly proportional to the voltage and inversely proportional to the resistance, provided the temperature remains constant. Resistance, the opposition to the flow of current, depends on factors like material, length, and temperature. Moving on to Kirchhoff’s Laws, they include Kirchhoff’s Current Law (KCL), which states that the sum of currents entering a junction equals the sum of currents leaving it, and Kirchhoff’s Voltage Law (KVL), which states that the sum of the potential differences (voltages) in any closed loop of a circuit is zero. These laws are essential for analyzing complex circuits. The Wheatstone Bridge is a circuit used to measure an unknown resistance by balancing two legs of a bridge circuit. The principle relies on the fact that the ratio of resistances in one leg equals the ratio in the other when the bridge is balanced, allowing for accurate measurement. Finally, the Potentiometer is an instrument used to measure the potential difference (voltage) without drawing current from the circuit. It operates on the principle that the potential drop across a uniform resistance is directly proportional to the length of the conductor, and it is used to compare the EMF of different sources or measure voltage accurately by setting up a balanced condition. These concepts form the foundation for understanding electrical circuits and their behavior.

3. Magnetic Effects of Current and Magnetism

Key Topics to Focus: Biot-Savart law, Ampere’s circuital law, Moving coil galvanometer, Magnetic properties of materials.
Important Viva Questions:
Q. State Biot-Savart law.
Q. What is the working principle of a moving coil galvanometer?
Q. Differentiate between diamagnetic and ferromagnetic materials.
Q. Explain the concept of magnetic field lines.

Key Points to Discuss in Viva:
In a viva, when discussing the Biot-Savart Law, you should explain that it describes the magnetic field produced by a current-carrying conductor. According to the law, the magnetic field at a point due to a small segment of current is directly proportional to the current and the length of the segment and inversely proportional to the square of the distance from the point to the segment. The magnetic field is also directed perpendicular to both the current element and the line connecting the element to the point. Moving to Ampere’s Circuital Law, this law relates the magnetic field in a closed loop to the current passing through the loop. It states that the line integral of the magnetic field around a closed path is proportional to the total current enclosed by the path, given by the formula ∮B⋅dl = μ0I, where μ0 is the permeability of free space. The Moving Coil Galvanometer is a sensitive instrument used for measuring small electrical currents, consisting of a coil suspended in a magnetic field. The deflection of the coil is proportional to the current passing through it, and the device can be converted into an ammeter or voltmeter by adding appropriate shunt resistors or a multiplier. Lastly, Magnetic Properties of Materials are categorized based on how they respond to external magnetic fields. Materials can be diamagnetic (slightly repel magnetic fields), paramagnetic (slightly attract magnetic fields), or ferromagnetic (strongly attract magnetic fields and can retain magnetization). These properties are crucial in understanding the behavior of materials in the presence of a magnetic field and their applications in devices like magnets and magnetic storage.

4. Electromagnetic Induction and Alternating Current

Key Topics to Focus: Faraday’s laws of electromagnetic induction, Lenz’s law, AC generator and transformer, RMS and peak values of AC.
Important Viva Questions:

    1. State Faraday’s laws of electromagnetic induction.
    2. What is Lenz’s law?
    3. How does a transformer work?
    4. What do you understand by the term RMS value?

Key Points to Discuss in Viva:
In a viva, when discussing Faraday’s Laws of Electromagnetic Induction, you should explain that Faraday’s First Law states that a change in the magnetic flux through a closed loop induces an electromotive force (EMF) in the loop. The Second Law quantifies this induced EMF, stating that it is proportional to the rate of change of magnetic flux, given by ϵ=−dΦ/dt . The negative sign represents the direction of the induced EMF, as described by Lenz’s Law, which states that the direction of the induced current opposes the change in magnetic flux, ensuring the conservation of energy. Moving to the AC Generator, this device converts mechanical energy into electrical energy through electromagnetic induction. As a coil rotates in a magnetic field, an alternating EMF is induced, and the output current alternates sinusoidally. The AC Transformer works on the principle of electromagnetic induction to step up or step down AC voltages. It consists of two coils, a primary and a secondary coil, wound on a common core. The transformer’s operation is based on the mutual induction between the coils, where the voltage ratio is proportional to the turns ratio of the coils. Lastly, when discussing RMS (Root Mean Square) and Peak Values of AC, you should note that RMS value represents the effective value of alternating current or voltage, which gives the same power as a DC circuit. The RMS value of a sinusoidal AC is Vpeak(sqrt{2}), where Vpeak is the maximum or peak value. The RMS value is essential for calculating power in AC circuits, as it reflects the energy delivered by the alternating current. These concepts are fundamental in understanding the behavior and applications of alternating currents and electromagnetic induction.

5. Optics

Key Topics to Focus: Reflection, refraction and total internal reflection, Lens formula and magnification in Ray Optics. Wave optics: Young’s double-slit experiment, Polarization and its applications.
Important Viva Questions:

    • What is total internal reflection? Give an example.
    • State and explain the lens maker’s formula.
    • What is interference of light?
    • How does polarization occur in light waves?

Key Points to Discuss in Viva:
In a viva, when discussing Reflection, you should explain that it occurs when light strikes a surface and bounces back, following the law of reflection, which states that the angle of incidence is equal to the angle of reflection. Refraction is the bending of light when it passes from one medium to another due to a change in its speed, described by Snell’s Law, n1sin⁡θ1 = n2.sin⁡θ2 , where n1 and n2 are the refractive indices of the two media. Total Internal Reflection occurs when light moves from a denser to a rarer medium at an angle greater than the critical angle, causing the light to be completely reflected inside the denser medium. Next, the Lens Formula is a mathematical relationship used to describe image formation by lenses: 1/f = 1/v − 1/u , where f is the focal length, v is the image distance, and u is the object distance. The Magnification produced by a lens is given by the ratio of the image height to the object height, also equal to the ratio of the image distance to the object distance, M = hi/ho = v/u. Moving on to Wave Optics, the Young’s Double-Slit Experiment demonstrates the wave nature of light, showing interference patterns formed when light passes through two slits. The spacing between bright or dark fringes is determined by the wavelength of the light and the distance between the slits. Polarization refers to the orientation of light waves in a particular direction, typically achieved through filters or reflection. Polarization has several applications, such as reducing glare in sunglasses, improving contrast in LCD screens, and in optical communication systems. These fundamental concepts in optics help explain the behavior of light and its interaction with various materials and mediums.

6. Dual Nature of Radiation and Matter

Key Topics to Focus: Photoelectric effect, Einstein’s photoelectric equation, Wave-particle duality, De Broglie wavelength.
Important Viva Questions:

    • What is the photoelectric effect?
    • State Einstein’s equation for the photoelectric effect.
    • Explain wave-particle duality.
    • What is De Broglie’s hypothesis?

Key Points to Discuss in Viva:
In a viva, when discussing the Photoelectric Effect, you should explain that it refers to the phenomenon where electrons are ejected from a material, typically a metal, when it is exposed to light of a certain frequency. This effect was crucial in establishing the particle nature of light. According to Einstein’s Photoelectric Equation, the energy of the emitted electrons is given by Ek = hf − ϕ, where E_k is the kinetic energy of the emitted electron, hf is the energy of the incident photon, and ϕ\phiϕ is the work function (the minimum energy required to eject an electron from the material). This equation confirmed that light behaves as discrete packets of energy called photons, with energy proportional to their frequency. Moving to Wave-Particle Duality, this concept suggests that light and matter exhibit both wave-like and particle-like properties. While light can demonstrate interference and diffraction patterns (wave-like behavior), it can also cause the ejection of electrons in the photoelectric effect, demonstrating particle-like behavior. This duality is fundamental in quantum mechanics. Finally, De Broglie’s Wavelength introduces the idea that all matter, including particles like electrons, has an associated wavelength, given by λ=h/mv, where λ is the wavelength, h is Planck’s constant, m is the mass, and v is the velocity of the particle. This wavelength is most noticeable for very small particles, like electrons and is a key concept in quantum mechanics, explaining phenomena such as electron diffraction. These concepts highlight the evolution of our understanding of the nature of light and matter at the quantum level.

7. Atoms and Nuclei

Key Topics to Focus: Bohr’s model of the atom, Radioactivity and its laws, Nuclear reactions and binding energy.
Important Viva Questions:

    1. State the postulates of Bohr’s atomic model.
    2. What are α, β, and γ radiations?
    3. Define binding energy.
    4. Explain the concept of mass defect in nuclear reactions.

Key Points to Discuss in Viva:
In a viva, when discussing Bohr’s Model of the Atom, you should explain that it was proposed to address the limitations of Rutherford’s model, specifically the stability of electrons in orbits. Bohr’s model suggests that electrons orbit the nucleus in fixed, quantized orbits without radiating energy and they can only move between these orbits by absorbing or emitting discrete amounts of energy (photons). The energy of these orbits is quantized and given by En = − 13.6/n² eV, where n is the principal quantum number. Next, Radioactivity refers to the spontaneous emission of radiation from unstable nuclei. This can include alpha (alphaα), beta (β) and gamma (γ) emissions. Radioactive decay follows certain laws, particularly the law of radioactive decay, which states that the rate of decay is proportional to the number of undecayed nuclei, and the half-life is the time required for half of the nuclei in a sample to decay. Understanding Nuclear Reactions involves processes where atomic nuclei change, such as fission (splitting of a heavy nucleus) or fusion (combining light nuclei). These reactions release vast amounts of energy, and the binding energy of a nucleus is the energy required to disassemble a nucleus into its constituent protons and neutrons. The binding energy per nucleon gives insight into the stability of a nucleus: a higher binding energy indicates greater stability. The energy released in nuclear fission or fusion comes from the difference in the binding energies of the reactants and products. These concepts are fundamental in understanding atomic structure, nuclear energy and the stability of matter at the nuclear level.

8. Electronic Devices

Key Topics to Focus: Semiconductors and their types, Diodes and their applications, Transistors and their working, Logic gates.
Important Viva Questions:

    • What is the difference between intrinsic and extrinsic semiconductors?
    • Explain the working of a p-n junction diode.
    • What are logic gates? Explain AND and OR gates.
    • How is a transistor used as an amplifier?

Key Points to Discuss in Viva:
In a viva, when discussing Semiconductors and Their Types, you should explain that semiconductors are materials with conductivity between conductors and insulators. They are categorized into intrinsic and extrinsic semiconductors. Intrinsic semiconductors are pure materials like silicon or germanium, where the number of free electrons equals the number of holes (positive charge carriers). Extrinsic semiconductors are created by adding impurities to intrinsic semiconductors, and they are further divided into n-type (with excess electrons) and p-type (with excess holes) semiconductors. Moving on to Diodes, you should explain that a diode is a semiconductor device that allows current to flow in one direction only, functioning as a rectifier. The most common type is the PN junction diode, where current flows easily from the p-side to the n-side but is blocked in the reverse direction. Diodes have various applications such as in rectifiers, voltage regulators, and light-emitting diodes (LEDs). Transistors are crucial semiconductor devices used for amplification and switching. A bipolar junction transistor (BJT) consists of three layers: emitter, base and collector. When a small current at the base controls a larger current between the collector and emitter, making it useful in amplifiers and switching circuits. Field-effect transistors (FETs) operate differently, using an electric field to control the flow of current. Finally, Logic Gates are fundamental building blocks of digital circuits, used to perform logical operations. The basic gates include AND, OR, NOT, NAND, NOR, XOR and XNOR, which manipulate binary inputs to produce specific outputs, enabling the creation of complex digital systems such as computers and calculators. These semiconductor devices and logic gates are essential in modern electronics, communication, and computing technologies.

How to Prepare for Class 12 Physics Viva Questions

The Class 12 Physics viva is an important part of the CBSE practical exams. It tests your understanding of experiments and basic concepts. To prepare, focus on topics like Ohm’s law, optics, and electromagnetic induction. Revise the theory behind your practical experiments and practice answering common viva questions. Use a Physics Lab Manual to understand setups and errors. Downloading a Physics Viva Questions PDF or referring to a CBSE Class 12 Practical Exam Guide can help. Stay confident, answer clearly and keep your responses concise. With preparation, you can easily perform well in the Physics Practical Viva.

Tips for Viva Success
    • Clarity of Concepts: Focus on understanding the fundamental concepts rather than memorizing definitions.
    • Lab Practical Understanding: Be thorough with your practical experiments, as viva questions often relate to them.
    • Confidence Matters: Answer confidently, even if you are unsure. It leaves a positive impression.
    • Revise Formulae: Physics vivas often include formula-based questions.
    • Practice Common Questions: Prepare the sample questions provided above for fluency.

    By following this guide and practicing diligently, you will be well-equipped to excel in your viva exams.

How Many Questions Are Asked in Viva?

The number of questions asked in a viva exam for Class 12th Physics depends on the examiner, the time available, and the depth of your responses. Typically, viva voice for Physics practical exams includes 5 to 10 questions, covering both theoretical concepts and practical experiments.

What are the Key Chapters for Viva questions in 12th Physics?

Electrostatics, Current Electricity, Magnetic Effects of Current and Magnetism, Electromagnetic Induction and Alternating Current, Optics, Dual Nature of Radiation and Matter, Atoms and Nuclei, Electronic Devices. Each of these chapters holds high importance for viva as they form the core of both theoretical and practical physics. Below, we elaborate on these chapters, discuss important concepts, and include relevant questions.