Physics Question Paper
Class 12
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 21 multiple choice questions of 1 mark each.
- Section B contains 8 questions of 2 marks each. (Optional numerical in 2 questions)
- Section C contains 6 questions of 3 marks each. (Optional numerical in 2 questions)
- Section D contains 3 questions of 5 marks each. (Optional questions for all 5-mark questions)
- Use of calculators is not permitted.
Section A: Multiple Choice Questions (1 Mark each)
- The SI unit of electric charge is:
- a) Coulomb
- b) Joule
- c) Newton
- d) Volt
- The electric field inside a conductor is:
- a) Constant
- b) Zero
- c) Infinity
- d) Variable
- According to Coulomb's law, the force between two charges is:
- a) Directly proportional to the product of the charges
- b) Inversely proportional to the product of the charges
- c) Directly proportional to the square of the distance between the charges
- d) Inversely proportional to the square of the distance between the charges
- Which of the following is the correct formula for drift velocity?
- a) vd = I/nqA
- b) vd = q/nIA
- c) vd = A/nIq
- d) None of the above
- The SI unit of resistivity is:
- a) Ohm
- b) Ohm-meter
- c) Volt
- d) Ampere
- Which of the following is a scalar quantity?
- a) Electric field
- b) Electric potential
- c) Force
- d) Magnetic field
- Magnetic flux through a surface is given by:
- a) φ = B . A
- b) φ = B × A
- c) φ = B/A
- d) φ = A × E
- The device used to measure current in a circuit is:
- a) Voltmeter
- b) Ammeter
- c) Galvanometer
- d) Potentiometer
- Ampere’s Circuital Law is related to:
- a) Electrostatic field
- b) Magnetic field
- c) Gravitational field
- d) Nuclear force
- The SI unit of magnetic field strength is:
- a) Tesla
- b) Henry
- c) Joule
- d) Coulomb
- What is the formula for the EMF induced in a rotating coil?
- a) e = NBA
- b) e = NAB sinθ
- c) e = NBA cosθ
- d) e = NAB cosθ
- The phenomenon of opposing induced EMF in a coil due to change in magnetic flux is called:
- a) Mutual Inductance
- b) Self Inductance
- c) Eddy Current
- d) Faraday’s Law
- Displacement current is produced in:
- a) Electric circuits
- b) Magnetic circuits
- c) Dielectric media
- d) Conductors
- The speed of electromagnetic waves in a vacuum is:
- a) 3 × 108 m/s
- b) 3 × 106 m/s
- c) 3 × 104 m/s
- d) None of the above
- The unit of capacitance is:
- a) Farad
- b) Henry
- c) Ohm
- d) Coulomb
- Lenz’s law gives:
- a) Direction of induced current
- b) Magnitude of induced current
- c) Both direction and magnitude of induced current
- d) None of the above
- The source of electromagnetic waves is:
- a) Accelerating charges
- b) Static charges
- c) Moving magnets
- d) Magnetic dipoles
- In a transformer, the energy loss due to the resistance of wires is called:
- a) Hysteresis loss
- b) Copper loss
- c) Eddy current loss
- d) Dielectric loss
- A moving coil galvanometer is used to measure:
- a) Voltage
- b) Current
- c) Electric field
- d) Magnetic field
- Which of the following is not a primary component of electromagnetic waves?
- a) Electric field
- b) Magnetic field
- c) Gravitational field
- d) None of the above
- The power factor of a pure resistor is:
- a) 1
- b) 0
- c) Infinity
- d) None of the above
Section B: Short Answer Questions (2 Marks each)
- State and explain Gauss’s law in electrostatics. Or A charge of 2 × 10-6 C is placed in a uniform electric field of 5 × 105 N/C. Find the force acting on the charge.
- Derive the relation between current density and electric field.
- What is the principle of superposition in the context of forces between charges? Or Find the equivalent resistance of two resistors of 5 Ω and 10 Ω connected in parallel.
- Explain the concept of self-inductance and its unit.
- Discuss the energy stored in a capacitor and derive the expression for it.
- What is the function of a capacitor in an AC circuit?
- Discuss the properties of electromagnetic waves.
- Explain Faraday's Law of Electromagnetic Induction.
Section C: Long Answer Questions (3 Marks each)
- Derive the formula for the capacitance of a parallel plate capacitor. Or A capacitor of 10 μF is connected to a 200 V battery. Calculate the energy stored in the capacitor.
- Explain the working of a moving coil galvanometer and derive its sensitivity.
- Derive the expression for the magnetic field at a point due to a long straight current-carrying conductor.
- Explain the phenomenon of resonance in an LCR circuit and its significance. Or In a series LCR circuit, the value of resistance is 10 Ω, inductance is 0.5 H, and capacitance is 100 μF. Calculate the resonant frequency.
- Discuss the displacement current and its role in Maxwell’s equations.
- Derive the formula for the induced EMF in a coil rotating in a magnetic field.
Section D: Long Answer Questions (5 Marks each)
- Derive the expression for the electric field due to a uniformly charged infinite plane sheet using Gauss’s law. Or A point charge of 5 μC is located at the origin. Calculate the electric field intensity at a distance of 10 cm from the charge.
- Magnetic fields are produced by moving electric charges. When a current flows through a conductor, it generates a magnetic field around it. The right-hand thumb rule helps in determining the direction of the magnetic field around a current-carrying conductor. Magnetic fields also influence nearby current-carrying conductors, producing forces between them. Parallel conductors carrying current in the same direction attract each other, while those carrying current in opposite directions repel each other.
- Explain how the right-hand thumb rule can be used to determine the direction of the magnetic field around a straight current-carrying conductor.
- What is the nature of the force between two parallel current-carrying conductors when they carry currents in the same direction? Why does this happen?
- What happens when the currents in two parallel conductors flow in opposite directions? Explain the reason behind this behavior.
- Describe how the magnetic field produced by a current-carrying conductor can affect nearby objects or conductors.
- Discuss the significance of the force between current-carrying conductors in defining the unit of current, the ampere.
- Explain the difference between diamagnetic, paramagnetic, and ferromagnetic materials based on their response to an external magnetic field.
- Why do ferromagnetic materials retain their magnetism even after the external field is removed?
- Give an example of a diamagnetic material and describe its behavior in a magnetic field.
- How do paramagnetic materials behave differently from ferromagnetic materials in the presence of a magnetic field?
- Discuss an application of ferromagnetic materials in everyday life and explain how their magnetic properties are useful.
- Explain the working of a transformer. Derive the relation between the primary and secondary voltages and currents. Or A transformer has 500 turns in its primary coil and 1000 turns in its secondary coil. If the input voltage is 220 V, calculate the output voltage.
Magnetic materials are classified into three categories: diamagnetic, paramagnetic, and ferromagnetic. Diamagnetic materials create an opposing magnetic field when placed in an external magnetic field, leading to weak repulsion. Paramagnetic materials have unpaired electrons that cause weak attraction in the presence of a magnetic field, but this effect disappears when the external field is removed. Ferromagnetic materials, like iron, have strong magnetic properties due to aligned domains and can retain their magnetism even after the external field is removed.
