50 Most Repeated Physics MCQs: Class 12 CBSE

Solved & Optimized for Board Exams 2026

All questions follow the latest CBSE MCQ pattern. Click the "Solution" dropdown to check your accuracy.

Unit 1: Electrostatics & Current Electricity

Q1. A dipole is placed in a uniform electric field. It experiences:
(a) Force only (b) Torque only (c) Both force and torque (d) Neither force nor torque

उत्तर (Solution)

Ans: (b) Torque only. In a uniform field, net force is zero ($qE - qE$), but since the forces act at different points, they produce torque.

Q2. If the distance between two charges is doubled, the electrostatic force becomes:
(a) 1/2 times (b) 2 times (c) 1/4 times (d) 4 times

उत्तर (Solution)

Ans: (c) 1/4 times. $F \propto 1/r^2$. So, doubling $r$ makes $F$ one-fourth.

Q3. Which of the following is the unit of Electric Flux?
(a) $V/m$ (b) $V \cdot m$ (c) $N/C$ (d) $Wb$

उत्तर (Solution)

Ans: (b) $V \cdot m$. $\Phi = E \cdot A$, units are $(V/m) \cdot m^2 = V \cdot m$.

Q4. Drift velocity $v_d$ varies with electric field $E$ as:
(a) $v_d \propto E$ (b) $v_d \propto E^2$ (c) $v_d \propto 1/E$ (d) Constant

उत्तर (Solution)

Ans: (a) $v_d \propto E$. From $v_d = (eE/m)\tau$.

Q5. Specific resistance (Resistivity) of a conductor depends on:
(a) Length (b) Area (c) Temperature/Material (d) All of these

उत्तर (Solution)

Ans: (c) Temperature and Material. It is independent of dimensions ($L$ and $A$).

Unit 2: Magnetic Effects of Current

Q6. The magnetic field at the center of a circular loop is:
(a) $\mu_0 I / 2R$ (b) $\mu_0 I / 2\pi R$ (c) $\mu_0 I / 4\pi R$ (d) Zero

उत्तर (Solution)

Ans: (a) $\mu_0 I / 2R$. Standard Biot-Savart application.

Q7. A charge moving parallel to a magnetic field experiences:
(a) Max force (b) Min force (c) Zero force (d) Constant torque

उत्तर (Solution)

Ans: (c) Zero force. $F = qvB\sin\theta$. For parallel, $\theta = 0$, so $\sin 0 = 0$.

Q8. The SI unit of Magnetic Dipole Moment is:
(a) $A/m$ (b) $A \cdot m^2$ (c) Tesla (d) $Wb/m^2$

उत्तर (Solution)

Ans: (b) $A \cdot m^2$. From $M = I \cdot A$.

Q9. Lenz's Law is a consequence of the law of conservation of:
(a) Charge (b) Mass (c) Momentum (d) Energy

उत्तर (Solution)

Ans: (d) Energy. Work done against the opposing force is converted to electrical energy.

Q10. In a purely inductive AC circuit, current lags voltage by:
(a) $0$ (b) $45^\circ$ (c) $90^\circ$ (d) $180^\circ$

उत्तर (Solution)

Ans: (c) $90^\circ$. Current lags by $\pi/2$ in an inductor.

Unit 3: Optics (Ray & Wave)

Q11. The refractive index of water is 4/3. The speed of light in water is:
(a) $3 \times 10^8$ (b) $2.25 \times 10^8$ (c) $4 \times 10^8$ (d) $1.5 \times 10^8$ m/s

उत्तर (Solution)

Ans: (b) $2.25 \times 10^8$ m/s. $v = c/n = (3 \times 10^8) / (4/3) = 2.25 \times 10^8$.

Q12. Critical angle is maximum for which color?
(a) Violet (b) Blue (c) Yellow (d) Red

उत्तर (Solution)

Ans: (d) Red. $\sin i_c = 1/n$. Red has the smallest refractive index, so it has the largest critical angle.

Q13. In YDSE, if wavelength is doubled, fringe width becomes:
(a) Half (b) Double (c) Four times (d) Unchanged

उत्तर (Solution)

Ans: (b) Double. $\beta = \lambda D/d$. $\beta \propto \lambda$.

Q14. The power of a convex lens of focal length 25cm is:
(a) $+4 D$ (b) $-4 D$ (c) $+0.25 D$ (d) $-0.25 D$

उत्तर (Solution)

Ans: (a) $+4 D$. $P = 1/0.25 = +4 D$.

Unit 4: Modern Physics

Q15. The work function of a metal depends on:
(a) Intensity (b) Frequency (c) Nature of metal (d) Time of exposure

उत्तर (Solution)

Ans: (c) Nature of metal. It is a property of the material.

Q16. Energy of a photon of wavelength $\lambda$ is:
(a) $h\lambda$ (b) $hc/\lambda$ (c) $\lambda/hc$ (d) $h/c\lambda$

उत्तर (Solution)

Ans: (b) $hc/\lambda$. From $E = h\nu = hc/\lambda$.

Q17. The radius of the first orbit of Hydrogen is 0.53 Å. Radius of second orbit is:
(a) 1.06 Å (b) 1.59 Å (c) 2.12 Å (d) 4.24 Å

उत्तर (Solution)

Ans: (c) 2.12 Å. $r \propto n^2$. For $n=2$, $r$ becomes $4 \times 0.53 = 2.12$ Å.

Q18. In p-type semiconductors, majority carriers are:
(a) Electrons (b) Holes (c) Photons (d) Neutrons

उत्तर (Solution)

Ans: (b) Holes. Created by trivalent impurities.

Q19. The frequency of a full-wave rectifier output for 50Hz input is:
(a) 25Hz (b) 50Hz (c) 100Hz (d) 200Hz

उत्तर (Solution)

Ans: (c) 100Hz. Output frequency doubles in full-wave rectification.

Q20. Which EM wave has the highest frequency?
(a) Radio (b) Microwave (c) X-ray (d) Gamma Ray

उत्तर (Solution)

Unit 5: Electricity & Magnetism (Advanced)

Q21. A parallel plate capacitor has capacitance $C$. If the distance between the plates is halved, the new capacitance will be:
(a) $C/2$ (b) $2C$ (c) $4C$ (d) $C$

उत्तर (Solution)

Ans: (b) $2C$. Since $C = \epsilon_0 A / d$, halving $d$ doubles the capacitance.

Q22. Kirchhoff’s First Law (Junction Rule) is based on the conservation of:
(a) Energy (b) Charge (c) Momentum (d) Mass

उत्तर (Solution)

Ans: (b) Charge. Total current entering a junction must equal the current leaving it.

Q23. To convert a galvanometer into an ammeter, one should connect a:
(a) High resistance in series (b) Low resistance in parallel (c) Low resistance in series (d) High resistance in parallel

उत्तर (Solution)

Ans: (b) Low resistance in parallel. This low resistance is called a 'shunt'.

Q24. The magnetic susceptibility of a paramagnetic substance is:
(a) Small and positive (b) Small and negative (c) Large and positive (d) Zero

उत्तर (Solution)

Ans: (a) Small and positive. Paramagnetic materials are weakly attracted by fields.

Q25. Eddy currents are produced when:
(a) Metal is in steady B-field (b) Metal is in varying B-field (c) Current is DC (d) In a vacuum

उत्तर (Solution)

Ans: (b) Metal is in varying B-field. Changing flux induces circulating currents in the bulk.

Unit 6: AC Circuits & EM Waves

Q26. In a series LCR circuit at resonance, the power factor is:
(a) 0 (b) 0.5 (c) 1 (d) Infinity

उत्तर (Solution)

Ans: (c) 1. At resonance, $X_L = X_C$, so $Z = R$ and $\cos \phi = 1$.

Q27. Which of the following EM waves has the shortest wavelength?
(a) Microwaves (b) UV rays (c) Gamma rays (d) Radio waves

उत्तर (Solution)

Ans: (c) Gamma rays. They have the highest frequency and shortest wavelength.

Q28. The brilliance of a diamond is primarily due to:
(a) Interference (b) Diffraction (c) Total Internal Reflection (d) Polarization

उत्तर (Solution)

Ans: (c) Total Internal Reflection. The high refractive index leads to a small critical angle.

Q29. According to Huygens' Principle, light is a form of:
(a) Particles (b) Waves (c) Energy packets (d) None

उत्तर (Solution)

Ans: (b) Waves. It explains light propagation through wavefronts.

Q30. The Photoelectric effect proves the:
(a) Wave nature (b) Particle nature (c) Transverse nature (d) None

उत्तर (Solution)

Ans: (b) Particle nature. It shows light behaves as discrete photons.

Unit 7: Atomic & Nuclear Physics

Q31. The de-Broglie wavelength $\lambda$ of a particle with momentum $p$ is:
(a) $\lambda = h/p$ (b) $\lambda = hp$ (c) $\lambda = p/h$ (d) $\lambda = h^2/p$

उत्तर (Solution)

Ans: (a) $\lambda = h/p$. Basic matter-wave relation.

Q32. Which series of the Hydrogen spectrum lies in the visible region?
(a) Lyman (b) Balmer (c) Paschen (d) Brackett

उत्तर (Solution)

Ans: (b) Balmer. Transitions to $n=2$ energy level.

Q33. The ratio of radii of the first and second orbits of Hydrogen is:
(a) 1:2 (b) 1:4 (c) 1:8 (d) 4:1

उत्तर (Solution)

Ans: (b) 1:4. Since $r \propto n^2$.

Q34. In a p-type semiconductor, the majority charge carriers are:
(a) Electrons (b) Holes (c) Photons (d) Neutrons

उत्तर (Solution)

Ans: (b) Holes. Doped with trivalent impurities.

Q35. The depletion layer in a p-n junction consists of:
(a) Electrons (b) Holes (c) Immobile Ions (d) Protons

उत्तर (Solution)

Ans: (c) Immobile Ions. Free carriers recombine, leaving fixed ions.

Unit 8: Electronics & Communication

Q36. For a common-emitter amplifier, the phase difference between input and output is:
(a) $0^\circ$ (b) $90^\circ$ (c) $180^\circ$ (d) $270^\circ$

उत्तर (Solution)

Ans: (c) $180^\circ$. Input and output are in opposite phases.

Q37. Which of the following has the highest ionizing power?
(a) Alpha particles (b) Beta particles (c) Gamma rays (d) X-rays

उत्तर (Solution)

Ans: (a) Alpha particles. Due to high mass and $+2e$ charge.

Q38. The SI unit of electric potential is equivalent to:
(a) $J/C$ (b) $N/C$ (c) $J \cdot C$ (d) $N \cdot m$

उत्तर (Solution)

Ans: (a) $J/C$. Potential is work done per unit charge.

Q39. The resistance of an ideal voltmeter should be:
(a) Zero (b) Low (c) High (d) Infinite

उत्तर (Solution)

Ans: (d) Infinite. So it draws no current from the circuit.

Q40. A wire is stretched to double its length. Its new resistance will be:
(a) $2 \times$ (b) $4 \times$ (c) $8 \times$ (d) Same

उत्तर (Solution)

Ans: (b) $4 \times$. $R \propto L^2$ when volume is constant.

Unit 9: Magnetism & Matter

Q41. The magnetic field inside a long straight solenoid is:
(a) Zero (b) Uniform (c) Non-uniform (d) Infinite

उत्तर (Solution)

Ans: (b) Uniform. Field lines are parallel straight lines.

Q42. The angle of dip at the magnetic equator is:
(a) $0^\circ$ (b) $45^\circ$ (c) $90^\circ$ (d) $180^\circ$

उत्तर (Solution)

Ans: (a) $0^\circ$. B-field is horizontal at the equator.

Q43. A step-up transformer increases:
(a) Current (b) Voltage (c) Power (d) Frequency

उत्तर (Solution)

Ans: (b) Voltage. At the cost of decreasing current.

Q44. Displacement current arises due to a:
(a) Steady E-field (b) Varying E-field (c) Steady B-field (d) DC current

उत्तर (Solution)

Ans: (b) Varying E-field. $I_d = \epsilon_0 (d\Phi_E/dt)$.

Q45. For Total Internal Reflection, light must travel from:
(a) Rarer to Denser (b) Denser to Rarer (c) Air to Water (d) Vacuum to Glass

उत्तर (Solution)

Ans: (b) Denser to Rarer. Angle of incidence must exceed critical angle.

Q46. The focal length of a plane mirror is:
(a) Zero (b) Infinite (c) Negative (d) 25 cm

उत्तर (Solution)

Ans: (b) Infinite. Radius of curvature is infinite.

Q47. Intensity ratio of two sources is 9:1. Ratio of Max to Min intensity is:
(a) 9:1 (b) 4:1 (c) 3:1 (d) 16:1

उत्तर (Solution)

Ans: (b) 4:1. $a_1/a_2 = 3/1$. $I_{max}/I_{min} = (3+1)^2 / (3-1)^2 = 16/4 = 4$.

Q48. Which phenomenon proves light is a transverse wave?
(a) Interference (b) Diffraction (c) Polarization (d) Reflection

उत्तर (Solution)

Ans: (c) Polarization. Longitudinal waves cannot be polarized.

Q49. The energy equivalent of 1 atomic mass unit (amu) is:
(a) 931 MeV (b) $1.6 \times 10^{-19} J$ (c) $9.1 \times 10^{-31} J$ (d) 1 MeV

उत्तर (Solution)

Ans: (a) 931 MeV. From $E=mc^2$.

Q50. The Boolean expression for an 'AND' gate is:
(a) $Y = A+B$ (b) $Y = A \cdot B$ (c) $Y = \bar{A}$ (d) $Y = \overline{A \cdot B}$

उत्तर (Solution)

Ans: (b) $Y = A \cdot B$. Output is high only when both inputs are high.

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