22 free Physics MCQs written in the Class 12 Boards exam pattern, each with a step-by-step solution. Tap an option for instant feedback — no sign-up, no ads.
Revise with smart repetition →✍️ These are original practice questions written in the Class 12 Boards pattern for the Class 12 board exams (CBSE pattern) — not questions from any official past paper.
Q1. The SI unit of electric charge is the:
B. Coulomb — Electric charge is measured in coulombs (C), where 1 C = 1 A·s. The ampere is current, the volt is potential difference, and the farad is capacitance.
Q2. The production of an induced EMF in a coil due to a changing magnetic flux through it is called:
C. Electromagnetic induction — Faraday's law describes electromagnetic induction: a changing magnetic flux through a circuit induces an EMF proportional to the rate of change of flux.
Q3. A device used to step up or step down an alternating (AC) voltage is a:
A. Transformer — A transformer changes AC voltage using electromagnetic induction between two coils. A rectifier converts AC to DC; it cannot step voltage up or down.
Q4. In the electromagnetic spectrum, which of these has the longest wavelength?
D. Radio waves — Radio waves have the longest wavelength (and lowest frequency). Gamma rays have the shortest wavelength and highest frequency.
Q5. According to Coulomb's law, the electrostatic force between two point charges is inversely proportional to the:
B. Square of the distance between them — Coulomb's law: F = kq₁q₂/r². The force is directly proportional to the product of the charges and inversely proportional to the square of the distance r between them.
Q6. The type of lens used to correct myopia (short-sightedness) is a:
B. Concave lens — Myopia (short-sightedness) is corrected with a concave (diverging) lens, which moves the image back onto the retina. Hypermetropia is corrected with a convex lens.
Q7. The electric field just inside a charged, isolated conductor in electrostatic equilibrium is:
A. Zero everywhere inside — In electrostatic equilibrium, charges reside on the surface of a conductor and the net electric field everywhere inside the conductor material is zero.
Q8. When a dielectric slab is inserted to completely fill the gap between the plates of an isolated (disconnected from any battery) charged parallel-plate capacitor, the potential difference across the plates:
B. Decreases — For an isolated capacitor the charge Q is fixed. Inserting a dielectric increases capacitance C, and since V = Q/C, the potential difference decreases.
Q9. The drift velocity of free electrons in a metallic conductor carrying a steady current is typically of the order of:
D. 10^-4 m/s — Although electrons move randomly at high speeds, the net drift velocity in the direction of the field is very small, of the order of 10^-4 m/s (a fraction of a mm per second).
Q10. A charged particle moving with velocity v enters a uniform magnetic field B such that v is exactly parallel to B. The magnetic force on the particle is:
B. Zero — The magnetic force is F = qv×B = qvB sinθ. When v is parallel to B, θ = 0, so sinθ = 0 and the force is zero.
Q11. A material that is weakly repelled by an external magnetic field and has a relative permeability slightly less than 1 is classified as:
C. Diamagnetic — Diamagnetic materials are weakly repelled by magnetic fields and have relative permeability slightly less than 1 (magnetic susceptibility small and negative).
Q12. According to Lenz's law, the direction of an induced current in a circuit is always such that it:
B. Opposes the change in magnetic flux that produces it — Lenz's law states the induced current opposes the change in magnetic flux causing it, which is a consequence of conservation of energy.
Q13. In a series LCR circuit driven at its resonant frequency, the power factor of the circuit is:
C. 1 — At resonance the inductive and capacitive reactances cancel, the impedance is purely resistive, current and voltage are in phase, so the power factor cosφ = 1.
Q14. In an electromagnetic wave travelling through vacuum, the electric field vector E and the magnetic field vector B are oriented such that they are:
B. Mutually perpendicular and both perpendicular to the direction of propagation — In an EM wave, E and B are perpendicular to each other and each is perpendicular to the direction of propagation, making it a transverse wave.
Q15. Total internal reflection of light can occur only when light travels from:
B. A denser medium to a rarer medium at an angle greater than the critical angle — Total internal reflection requires light going from a denser to a rarer medium with the angle of incidence exceeding the critical angle, so no refracted ray escapes.
Q16. In Young's double-slit experiment, if the separation between the two slits is increased while all else is kept constant, the fringe width of the interference pattern:
B. Decreases — Fringe width β = λD/d is inversely proportional to the slit separation d, so increasing d decreases the fringe width.
Q17. In the photoelectric effect, increasing the intensity of incident light (while keeping its frequency above the threshold) increases:
B. The number of electrons emitted per second — Higher intensity means more photons per second, so more electrons are ejected per second (larger photocurrent). Maximum kinetic energy and stopping potential depend only on frequency, not intensity.
Q18. The energy of the electron in the second orbit (n = 2) of a hydrogen atom, given the ground-state energy is -13.6 eV, is:
C. -3.4 eV — In the Bohr model E_n = -13.6/n^2 eV. For n = 2, E = -13.6/4 = -3.4 eV.
Q19. The binding energy per nucleon is greatest for nuclei with mass number around 56 (iron region). This implies that these nuclei are:
B. The most stable, being hardest to break apart per nucleon — A higher binding energy per nucleon means the nucleons are more tightly bound, so nuclei near iron (A≈56) are the most stable.
Q20. In a p-n junction diode, the depletion region is a layer near the junction that is:
B. Depleted of free charge carriers and contains immobile ions — Diffusion of carriers across the junction leaves behind immobile charged ions and removes free carriers, forming a depletion region with an associated potential barrier.
Q21. A thin convex lens of power +5 D is placed in contact with a thin concave lens of power -2 D. The focal length of the combination is:
A. +33.3 cm (converging) — For thin lenses in contact, net power P = P1 + P2 = 5 + (-2) = +3 D. Focal length f = 1/P = 1/3 m ≈ +33.3 cm, and being positive it is converging.
Q22. The work done in moving a test charge between two points that lie on the same equipotential surface is:
B. Zero — On an equipotential surface the potential difference between any two points is zero, so W = qΔV = 0; no work is done in moving a charge along it.
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