CLASS XII PHYSICS
SEPTEMBER EXAMINATION • SAMPLE QUESTION PAPER 2
Time Allowed: 3 Hours | Maximum Marks: 70
GENERAL INSTRUCTIONS
- All questions are compulsory.
- The question paper carries 70 marks and is divided into four sections:
- Section A: 16 MCQs × 1 mark = 16 marks
- Section B: 6 questions × 2 marks = 12 marks
- Section C: 9 questions × 3 marks = 27 marks, including one case-study-based question
- Section D: 3 questions × 5 marks = 15 marks
- Attempt only one option where an internal choice is given.
- Use appropriate SI units and show necessary steps in numerical questions.
Useful Constants (where required):
c = 3 × 108 m/s |
me = 9.1 × 10−31 kg |
e = 1.6 × 10−19 C |
μ0 = 4π × 10−7 T m A−1 |
ε0 = 8.854 × 10−12 C2 N−1 m−2
SECTION A — MULTIPLE CHOICE QUESTIONS (16 × 1 = 16 MARKS)
Q1. Answer the following multiple-choice questions:
(i) The electric field at a distance r from an infinitely long straight uniformly charged wire is:
(A) inversely proportional to r
(B) inversely proportional to r2
(C) inversely proportional to r3
(D) independent of r
(ii) Which one of the following charges is NOT possible?
(A) 1.602 × 10−19 C
(B) 3.204 × 10−19 C
(C) 5.607 × 10−19 C
(D) 6.408 × 10−19 C
(iii) The direction of electric field vector at a point on the equatorial line of a dipole is:
(A) in the same direction of dipole moment
(B) in the opposite direction to the dipole moment
(C) towards the negative charge
(D) towards the positive charge
(iv) Name the physical quantity whose SI unit is joule per coulomb:
(A) Power
(B) Electric field
(C) Electric potential
(D) Dipole moment
(v) For linear dielectrics, the ratio of dielectric polarisation P to the applied electric field E is equal to:
(A) Mobility
(B) Dipole moment
(C) ε0 × Susceptibility
(D) Permittivity
(vi) In the absence of an electric field, the mean velocity of free electrons in a conductor at absolute temperature T is:
(A) Zero
(B) Independent of T
(C) Proportional to T
(D) Proportional to T2
(vii) Kirchhoff's first law (∑ I = 0 at a junction) deals with the conservation of:
(A) Energy
(B) Momentum
(C) Charge
(D) Angular momentum
(viii) Resistance of an ideal ammeter is:
(A) Infinity
(B) 100 Ω
(C) Zero
(D) 1 Ω
(ix) When a magnetic compass needle is carried near a straight wire carrying current:
(I) The straight wire causes a noticeable deflection in the compass needle.
(II) The alignment of the needle is tangential to an imaginary circle centered on the wire in a plane perpendicular to the wire.
(A) Only (I) is correct
(B) Only (II) is correct
(C) Both (I) and (II) are correct
(D) Neither (I) nor (II) is correct
(x) If the magnetic susceptibility of a material is 100, its relative permeability is:
(A) 100
(B) 99
(C) 101
(D) 10
(xi)
Assertion (A): Magnetic field lines do not intersect each other.
Reason (R): If magnetic field lines intersect, the magnetic field would not have a unique direction at the point of intersection.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(B) Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
(C) Assertion (A) is true and Reason (R) is false.
(D) Both Assertion (A) and Reason (R) are false.
(xii) In electromagnetic induction, the induced emf in a coil is independent of:
(A) change in the magnetic flux
(B) time of change of magnetic flux
(C) resistance of the circuit
(D) number of turns in the coil
(xiii) In a purely capacitive circuit, if the frequency of AC is doubled, the capacitive reactance will:
(A) get doubled
(B) become four times
(C) get halved
(D) remain constant
(xiv) At resonance, a series LCR AC circuit behaves like a:
(A) purely capacitive circuit
(B) purely resistive circuit
(C) purely inductive circuit
(D) LC circuit
(xv) Displacement current is produced due to:
(A) Constant electric field
(B) Constant magnetic field
(C) Changing electric field
(D) Changing magnetic field
(xvi)
Assertion (A): Electromagnetic waves are transverse in nature.
Reason (R): The electric and magnetic fields in electromagnetic waves are perpendicular to each other and to the direction of propagation.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
(B) Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
(C) Assertion (A) is true and Reason (R) is false.
(D) Both Assertion (A) and Reason (R) are false.
SECTION B — SHORT ANSWER QUESTIONS (6 × 2 = 12 MARKS)
Q2. Write Coulomb’s law in vector form and explain the terms involved. [2 Marks]
OR
State and explain Gauss's law in electrostatics. [2 Marks]
Q3. Define current density in a conductor. Mention its SI unit. [2 Marks]
Q4. The electrostatic potential at a point is 10 V. Find the work required to move a charge of 20 μC from infinity to that point. [2 Marks]
Q5. What is Lorentz force? Write the vector expression representing this force. [2 Marks]
Q6. The current in a circuit falls from 5.0 A to 0.0 A in 0.1 s. If an average emf of 200 V is induced, calculate the self-inductance of the circuit. [2 Marks]
OR
In an inductive AC circuit, the value of inductance is 0.2 H and the frequency of AC is 50 Hz. Calculate the inductive reactance. [2 Marks]
Q7. Write Ampere-Maxwell’s equation and explain the physical terms. [2 Marks]
SECTION C — SHORT ANSWER / CASE STUDY QUESTIONS (9 × 3 = 27 MARKS)
Q8. State the principle of superposition of electrostatic forces. Three equal positive charges are placed at three corners A, B, and C of a square ABCD. Sketch a diagram to show the resultant force on the charge at B. [3 Marks]
OR
Describe an experiment to demonstrate that there are two distinct types of electric charges using glass and plastic rods. [3 Marks]
Q9. Distinguish between polar and non-polar dielectrics. Give one example for each. [3 Marks]
Q10. Two point charges qA = 3 μC and qB = −3 μC are located 20 cm apart in vacuum. Find the magnitude and direction of the electric field at the midpoint O of the line AB joining the two charges. [3 Marks]
Q11. Derive an expression for the drift velocity of free electrons in a conductor in terms of relaxation time. [3 Marks]
Q12. State and explain Gauss's law in magnetism. What important property of magnetic monopoles does it signify? [3 Marks]
Q13. Explain with the help of a circuit diagram how a galvanometer is converted into an ammeter of a given range. [3 Marks]
OR
Explain with the help of a circuit diagram how a galvanometer is converted into a voltmeter of a given range. [3 Marks]
Q14. CASE STUDY-BASED QUESTION
A modern hospital relies on an uninterrupted AC power supply for operation theatres, intensive care units, and diagnostic equipment. During a power outage, an inverter converts DC from batteries into alternating current to ensure that critical equipment continues to function. The inverter generates an alternating voltage with a peak value of 325 V and a frequency of 50 Hz. Engineers monitor the RMS voltage, current, and power factor to ensure efficient power transmission and minimize energy losses. The maintenance team also studies the behaviour of resistive, inductive, and capacitive loads connected to the AC supply before selecting suitable transformers and protection devices.
(a) Why is RMS value used instead of peak value while specifying domestic AC supply? [1 mark]
(b) Calculate the RMS voltage if the peak voltage is 325 V. [1 mark]
(c) State any two advantages of AC over DC for long-distance power transmission. [1 mark]
Q15. What is resonance in a series LCR circuit? Obtain the expression for its resonant frequency. [3 Marks]
OR
Mention any three major sources of energy loss in a transformer and how they are minimized. [3 Marks]
Q16. A current loop of area 20 × 10−4 m2 carrying a current of 0.2 A is placed with its plane at an angle of 60° with a uniform magnetic field of strength 4 × 10−2 T. Calculate the torque exerted on the loop. [3 Marks]
SECTION D — LONG ANSWER QUESTIONS (3 × 5 = 15 MARKS)
Q17.
(a) Using Gauss's law, derive the expression for the electric field due to an infinitely long straight uniformly charged wire of linear charge density λ.
(b) Plot a graph showing the variation of electric field E with distance r from the wire.
OR
(a) Define capacitance of a capacitor.
(b) Derive the expression for the effective capacitance of two capacitors connected in series.
(c) Write two factors on which the capacitance of a parallel plate capacitor depends.
[5 Marks]
Q18.
(a) Derive the expression for the force per unit length between two long, straight, parallel current-carrying conductors.
(b) Hence, define the standard SI unit of current ('ampere').
OR
(a) With the help of a neat labelled diagram, explain the construction, principle, and working of a moving coil galvanometer.
(b) State the role of (i) radial magnetic field and (ii) soft iron core in a moving coil galvanometer.
[5 Marks]
Q19.
(a) An AC voltage v = v0 sin(ωt) is applied across a pure inductor of inductance L. Derive the expression for the instantaneous current and show that current lags voltage by π/2 radians.
(b) Draw the phasor diagram and voltage-current waveforms for this circuit.
OR
(a) Derive the expression for the impedance of a series LCR circuit connected to an AC source using a phasor diagram.
(b) Obtain the condition under which electrical resonance occurs and state the power factor at resonance.
[5 Marks]












