Class 12 Physics Question Paper Set 4
Time: 3 Hours
Maximum Marks: 70
General Instructions:
- All questions are compulsory.
- This question paper contains four sections: A, B, C, and D.
- Section A contains 15 multiple-choice questions of 1 mark each.
- Section B contains 7 questions of 2 marks each.
- Section C contains 7 questions of 3 marks each.
- Section D contains 3 questions of 5 marks each, including a comprehension-based question from Electromagnetic Induction.
- Internal choices are provided in two questions in Section B, one question in Section C, and one question in Section D.
- Use of calculators is not permitted.
- Wherever necessary, neat diagrams must be drawn.
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 field due to a uniformly charged spherical shell outside the shell is:
- a) Zero
- b) Proportional to the square of the distance from the center
- c) Proportional to the inverse square of the distance
- d) Proportional to the charge density
- A capacitor is charged by a battery and then disconnected. If the separation between the plates is increased, the capacitance:
- a) Increases
- b) Decreases
- c) Remains the same
- d) Becomes zero
- The drift velocity of electrons in a conductor is:
- a) Directly proportional to the applied electric field
- b) Inversely proportional to the electric field
- c) Proportional to the current squared
- d) Independent of the electric field
- The potential difference across a conductor is doubled. The current through it will:
- a) Be halved
- b) Remain the same
- c) Be doubled
- d) Be reduced to zero
- The force between two current-carrying conductors placed parallel to each other is:
- a) Attractive if the currents are in the same direction
- b) Repulsive if the currents are in the same direction
- c) Always repulsive
- d) Independent of the distance between them
- A magnetic field exerts no force on:
- a) A moving charge
- b) A stationary charge
- c) A current-carrying conductor
- d) A magnet
- The phenomenon of electromagnetic induction is:
- a) The generation of current due to a changing electric field
- b) The generation of EMF due to a changing magnetic flux
- c) The generation of magnetic flux by a current
- d) The production of heat by a current
- In a step-down transformer:
- a) The current is decreased and voltage is increased
- b) Both current and voltage are decreased
- c) The voltage is decreased and current is increased
- d) Both current and voltage remain constant
- The energy of electromagnetic waves is:
- a) Proportional to its frequency
- b) Proportional to its amplitude
- c) Inversely proportional to its wavelength
- d) Independent of frequency
- The refractive index of a medium depends on:
- a) Wavelength of light
- b) Temperature
- c) Angle of incidence
- d) Both a) and b)
- The electric field intensity at a point due to a dipole is inversely proportional to:
- a) \( r \)
- b) \( r^2 \)
- c) \( r^3 \)
- d) \( r^4 \)
- Lenz's law provides:
- a) The magnitude of the induced EMF
- b) The direction of the induced EMF
- c) Both magnitude and direction of the induced EMF
- d) None of the above
- The speed of electromagnetic waves in vacuum is:
- a) \( 2 \times 10^8 \, m/s \)
- b) \( 3 \times 10^8 \, m/s \)
- c) \( 1.5 \times 10^8 \, m/s \)
- d) \( 4 \times 10^8 \, m/s \)
- The unit of magnetic flux is:
-
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- a) Weber
- b) Tesla
- c) Henry
- d) Ampere
- In an AC circuit containing only a capacitor, the voltage leads the current by:
- a) 0°
- b) 90°
- c) 180°
- d) 270°
Section B: Short Answer Questions (2 Marks each)
- Derive the formula for the capacitance of a parallel plate capacitor with a dielectric between the plates.
- What is drift velocity? How is it related to current?
- State and explain Gauss's law. How is it applied to calculate the electric field of a uniformly charged spherical shell?
- Explain the working principle of a moving coil galvanometer.
- What is mutual inductance? Explain its significance in transformers. Or Explain Lenz's law with an example and show how it supports the law of conservation of energy.
- Write the significance of displacement current in Maxwell’s equations.
- What are the properties of electromagnetic waves? Discuss their role in communication.
Section C: Long Answer Questions (3 Marks each)
- Derive the expression for the energy stored in a capacitor. Or How does inserting a dielectric between the plates of a capacitor affect its capacitance? Explain.
- Explain the working of a potentiometer. How is it used to measure the internal resistance of a cell?
- Derive the expression for the magnetic field inside a current-carrying solenoid.
- Discuss the resonance in an LCR circuit. What is its practical significance in communication systems?
- Explain the principle and working of a step-up transformer. Or How does an AC generator use electromagnetic induction to produce alternating current?
- Explain the phenomenon of diffraction of light and its applications in optics.
- Describe how electromagnetic waves are generated by oscillating charges.
Section D: Long Answer Questions (5 Marks each)
- Derive the expression for the electric potential due to a dipole at a point on its axial line. Or Explain the behavior of capacitors when connected in series and parallel. Derive the expressions for their equivalent capacitances.
- Explain the interference of light and derive the expression for fringe width in Young's double-slit experiment. Or Discuss the diffraction of light through a single slit. Derive the conditions for maxima and minima.
Comprehension Question: Electromagnetic Induction (5 Marks)
Read the passage below carefully and answer the following questions:
Electromagnetic induction refers to the process by which an electromotive force (EMF) is generated when the magnetic flux linked with a conductor changes. Faraday's law of induction states that the magnitude of induced EMF is directly proportional to the rate of change of magnetic flux. Lenz’s law, which provides the direction of the induced current, asserts that the induced EMF opposes the change in magnetic flux, ensuring conservation of energy. This principle forms the foundation of many electrical devices such as transformers, electric generators, and induction motors.
For instance, in an electric generator, mechanical energy is converted into electrical energy by rotating a coil in a magnetic field, thus causing a continuous change in magnetic flux through the coil and inducing an alternating current (AC). Similarly, transformers are used to step up or step down AC voltage levels through electromagnetic induction, where the changing magnetic flux in the primary coil induces a voltage in the secondary coil.
- State Faraday’s law of electromagnetic induction and explain how it applies to the working of a transformer.
- Explain how Lenz’s law ensures the conservation of energy in electromagnetic induction.
- How does the rate of change of magnetic flux affect the induced EMF in a conductor? Justify your answer with Faraday’s law.
- What role does electromagnetic induction play in the working of an electric generator?
- If the number of turns in the secondary coil of a transformer is increased, what effect does this have on the induced EMF? Explain your answer.
