Class 12 Physics Question Paper Set 3
Time: 3 Hours
Maximum Marks: 70
General Instructions:
- All questions are compulsory.
- The question paper consists of four sections – A, B, C, and D.
- Section A contains 15 multiple choice questions of 1 mark each.
- Section B contains 8 questions of 2 marks each.
- Section C contains 6 questions of 3 marks each.
- Section D contains 3 questions of 5 marks each, including a comprehension-based question from Electromagnetic Induction.
- Internal choice is provided in some questions.
- Use of calculators is not permitted.
- Draw neat diagrams wherever necessary.
Unit-wise Question Distribution
Unit 1: Electrostatics (Total: 20 marks)
- 1 Mark Questions: 4 questions = 4 marks
- 2 Marks Questions: 3 questions = 6 marks
- 3 Marks Questions: 2 questions = 6 marks
- 5 Marks Questions: 1 question = 5 marks
Unit 2: Current Electricity (Total: 12 marks)
- 1 Mark Questions: 2 questions = 2 marks
- 2 Marks Questions: 2 questions = 4 marks
- 3 Marks Questions: 1 question = 3 marks
- 5 Marks Questions: 1 question = 3 marks
Unit 3: Magnetic Effects of Current & Magnetism (Total: 20 marks)
- 1 Mark Questions: 4 questions = 4 marks
- 2 Marks Questions: 2 questions = 4 marks
- 3 Marks Questions: 2 questions = 6 marks
- 5 Marks Questions: 1 question = 5 marks
Unit 4: Electromagnetic Induction & Alternating Current (Total: 12 marks)
- 1 Mark Questions: 3 questions = 3 marks
- 2 Marks Questions: 2 questions = 4 marks
- 3 Marks Questions: 1 question = 3 marks
- 5 Marks Questions: 1 question = 5 marks
Unit 5: Electromagnetic Waves (Total: 6 marks)
- 1 Mark Questions: 2 questions = 2 marks
- 2 Marks Questions: 1 question = 2 marks
- 3 Marks Questions: 1 question = 2 marks
Section A: Multiple Choice Questions (1 Mark each)
- The electric potential due to a point charge varies as:
- a) \( \frac{1}{r} \)
- b) \( \frac{1}{r^2} \)
- c) \( \frac{1}{r^3} \)
- d) Independent of \( r \)
- Two charges \( q_1 \) and \( q_2 \) are separated by a distance \( r \). The force between them is proportional to:
- a) \( q_1 \times q_2 \)
- b) \( \frac{q_1}{q_2} \)
- c) \( \frac{q_1 \times q_2}{r^2} \)
- d) \( \frac{q_1 + q_2}{r^2} \)
- The SI unit of electric dipole moment is:
- a) C/m
- b) C·m
- c) N·m
- d) V·m
- The energy stored in a capacitor is given by:
- a) \( \frac{1}{2}CV^2 \)
- b) \( CV^2 \)
- c) \( \frac{1}{2}\frac{V^2}{C} \)
- d) \( \frac{V^2}{C} \)
- The drift velocity of electrons in a conductor is:
- a) Proportional to the applied electric field
- b) Inversely proportional to the electric field
- c) Proportional to the square of the current
- d) Independent of the electric field
- The resistivity of a material depends on:
- a) Its length
- b) Its temperature
- c) Its cross-sectional area
- d) The applied voltage
- The magnetic field inside a long straight solenoid carrying current is:
- a) Zero
- b) Uniform and parallel to the axis
- c) Non-uniform and perpendicular to the axis
- d) Inversely proportional to the current
- A current-carrying conductor placed in a magnetic field experiences maximum force when:
- a) It is parallel to the field
- b) It is perpendicular to the field
- c) It makes an angle of 45° with the field
- d) The current is zero
- The unit of magnetic flux is:
- a) Tesla
- b) Weber
- c) Henry
- d) Ampere
- In a step-up transformer:
- a) The voltage is increased and current is decreased
- b) Both voltage and current are increased
- c) The voltage decreases and current increases
- d) Both voltage and current are decreased
- The direction of the induced current due to electromagnetic induction is given by:
- a) Faraday’s law
- b) Lenz’s law
- c) Ampere’s law
- d) Coulomb’s law
- The time period of an AC voltage source is 0.02 s. The frequency of the source is:
- a) 50 Hz
- b) 100 Hz
- c) 200 Hz
- d) 25 Hz
- The speed of electromagnetic waves in a vacuum is:
- a) 2 × 108 m/s
- b) 3 × 108 m/s
- c) 5 × 108 m/s
- d) 1 × 108 m/s
- Which of the following electromagnetic waves have the shortest wavelength?
- a) Gamma rays
- b) X-rays
- c) Ultraviolet rays
- d) Radio waves
- The energy of an electromagnetic wave is:
- a) Proportional to its frequency
- b) Proportional to its wavelength
- c) Independent of frequency
- d) Proportional to its amplitude
Section B: Short Answer Questions (2 Marks each)
- State and explain Gauss's law in electrostatics. How is it applied to a spherical shell? Or Explain the concept of electric potential energy for a system of two point charges.
- Derive the formula for the equivalent resistance of resistors connected in series.
- What is drift velocity? How is it related to the current flowing through a conductor?
- Explain the principle of the working of a cyclotron.
- What is mutual inductance? Explain its significance in transformers. Or Explain Lenz's law and how it follows the law of conservation of energy.
- Explain the significance of displacement current in Maxwell's equations.
- Describe how electromagnetic waves are produced by oscillating charges.
Section C: Long Answer Questions (3 Marks each)
- Derive the expression for the energy stored in a charged capacitor. Or What happens to the capacitance of a capacitor if a dielectric slab is inserted between its plates? Explain the physics behind it.
- Explain the working of a potentiometer and how it can be used to compare the EMF of two cells.
- Derive the expression for the magnetic field inside a solenoid carrying current.
- Explain the phenomenon of resonance in an LCR circuit. What are its practical applications?
- Discuss the principle and working of a transformer. Or Explain how electromagnetic induction is used in an AC generator.
- Discuss the properties of electromagnetic waves. Why can they travel through a vacuum?
Section D: Long Answer Questions (5 Marks each)
- Derive the expression for the electric potential due to an electric dipole at a point on its axial line. Or Explain how capacitors behave when connected in series and parallel. Derive the expressions for their equivalent capacitances.
- Explain the principle of interference of light. Derive the expression for fringe width in Young's double-slit experiment. Or Describe the diffraction of light and its practical applications.
Comprehension Question: Electromagnetic Induction (5 Marks)
Read the passage below carefully and answer the following questions:
Electromagnetic induction is the process by which a changing magnetic flux induces an electromotive force (EMF) in a conductor. Faraday’s law states that the magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux. Lenz’s law explains that the direction of the induced EMF opposes the change in flux, ensuring the conservation of energy. This principle is used in various electrical devices such as transformers, electric generators, and induction motors.
In an electric generator, a coil rotates in a magnetic field, causing the magnetic flux through the coil to change continuously. As a result, an alternating current (AC) is generated in the coil. Similarly, transformers work on the principle of electromagnetic induction to convert alternating current from one voltage level to another through the use of primary and secondary coils.
- State Faraday’s law of electromagnetic induction. How does it apply to the working of an electric generator?
- Explain Lenz’s law. How does it ensure the conservation of energy in electromagnetic induction?
- Describe how electromagnetic induction is used in transformers to step up or step down voltage levels.
- If the rate of change of magnetic flux through a coil is doubled, what happens to the induced EMF? Justify your answer.
- In an induction motor, how does electromagnetic induction generate mechanical energy?
