CBSE Physics Class 12 Answer Key 2025 (Available): Unofficial Key PDF

Interested students can access the CBSE Physics Class 12 Answer Key 2025 available here.

Mohith Kumar

Updated on -Feb 21, 2025 | 06:36 PM IST

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CBSE Physics Class 12 Answer Key 2025: The Central Board of Secondary Education (CBSE) successfully concluded the CBSE Class 12 Physics Examination 2025 today, February 21, 2025. The exam was held from 10:30 AM to 1:30 PM. Students who appeared for the CBSE Class 12 Physics Examination 2025 and are eager to know the answers for the questions asked in the examination can check the CBSE Physics Class 12 Answer Key 2025 available here with the Unofficial Key PDF.

CBSE 12th Physics Exam 2025 (Live Update): Question Paper, Exam Analysis, Answer Key

CBSE Physics Class 12 Answer Key 2025: Question and Answers

The CBSE Physics Class 12th Answer Key 2025 for questions asked in the examination are listed below.

Question 1: The electromagnetic waves used in radar system are:
Answer: Microwaves

Question 2: The figure shows variation of current (I) with time (t) in four devices P, Q, R and S. The device in which an alternating current flows is
Answer: S

Question 3: In Young's double-slit experiment, the fringe width is found to be ẞ. If the entire apparatus is immersed in a liquid of refractive index μ, the new fringe width will be:
Answer: ẞ/μ

Question 4: Photons of energy 4.3 eV are incident on a photosensitive surface of work function 2.3 eV. The stopping potential for photoelectrons is:
Answer: 2.3 eV

Question 5: Which of the following statements is not true for nuclear forces?
(a) They are stronger than Coulomb forces.
(b) They have about the same magnitude for different pairs of nucleons.
(c) They are always attractive.
(d) They saturate as the separation between two nucleons increases.
Answer: (b)They have about the same magnitude for different pairs of nucleons.

Question 6: A point charge q is kept at a distance r from an infinitely long straight wire with charge density λ. The magnitude of the electrostatic force experienced by charge q is:
Answer: qλ/2π E 0 r

Question 7: The ratio of the magnitude of magnetic moment to that of angular momentum, of an electron revolving around the nucleus in a hydrogen atom is:
Answer: Zero

Question 8: Which one of the following has a negative value of susceptibility?
Answer: Lead

Question 9: The difference in mass of 7 X nucleus and total mass of its constituent nucleons is 21.00 u. The binding energy per nucleon for this nucleus is equal to the energy equivalent of:
Answer: 3.5 u

Question 10: The threshold voltage for a p-n junction diode used in the circuit is 0·7 V. The type of biasing and current in the circuit are:
Answer: Reverse biasing, 2 mA

Question 11: The kinetic energy of an alpha particle is four times the kinetic energy of a proton. The ratio will be the wavelength associated with them.
Answer: 1/16

Question 12: A glass slab of thickness 6 cm is placed over a paper. The shift in the letters printed on the paper will be
Answer: 2 cm

Question 13: The dimension (ue)-1 where e is the permittivity and u is permeability of a medium are:
Answer: option B

Question 14: Which one of the following statements is correct?
Electric field due to static charges is
(A) conservative and field lines do not form closed loops.
(B) conservative and field lines form closed loops.
(C) non-conservative and field lines do not form closed loops.
(D) non-conservative and field lines form closed loops.
Answer: c) non-conservative and field lines do not form closed loops.

Question 15: A material pushed out when placed in a uniform magnetic field. The material is:
Answer: Paramagnetic

Question 16: A 1 cm straight segment of a conductor carrying 1 A current in x direction lies symmetrically at origin of Cartesian coordinate system. The magnetic field due to this segment at point (1m, 1m, 0) is:
Answer: -1.0 * 10 -9 k̂ T

Question 17: The plane face of a planoconvex lens is silvered. The refractive index of material and radius of curvature of the curved surface of the lens are n and R respectively. This lens will behave as a concave mirror of focal length.
Answer: nR

Question 18: When the resistance measured between p and n ends of a p-n junction diode is high, it can act as a/an -
Answer: inductor

Question 19: Atomic spectral emission lines of hydrogen atom are incident on a zinc surface. The lines which can emit photoelectrons from the surface are members of:
Answer: Neither Balmer, nor Paschen nor Lyman series

Question 20: The number of turns between different pairs of output terminals are shown for a step-up transformer. Input voltage of 20 V is applied between A and B. Between which two terminals will the output be 120 V?
Answer: P and R

Question 21: A soft iron rod X is allowed to fall on the two poles of a U shaped permanent magnet as shown in figure. A coil is wrapped over one arm of the U shaped magnet. During the fall of the rod, the current in the coil will be:
Answer: Clock-wise Current

Question 22: Consider two identical dipoles D ₁and D ₂. Charges -q and q of dipole D ₁are located at (0, 0) and (a, 0) and that of dipole D ₂at (0, a) and (0, 2a) in x-y plane, respectively. The net dipole moment of the system is:
Answer: qa(î + ĵ)

Question 23: Atomic spectral emission lines of hydrogen atom are incident on a zinc surface. The lines which can emit photoelectrons from the surface are members of
Answer: Lyman Series

Question 24: A tub is filled with a transparent liquid to a height of 30.0 cm. The apparent depth of a coin lying at the bottom of the tub is found to be 16.0 cm. The speed of light in the liquid will be
Answer: 2.0 * 10 8 m s -1

Question 25: A transformer is connected to a 200 V ac source. The transformer supplies 3000 V to a device. If the number of turns in the primary coil is 450, then the number of turns in its secondary coil is -
Answer: 30

Question 26: In the figure X is a coil wound over a hollow wooden pipe. A permanent magnet is pushed at a constant speed v from the right into the pipe and it comes out at the left end of the pipe. During the entry and the exit of the magnet, the current in the wire YZ will be from
Answer: Z to Y and then Y to Z

Question 27: The magnetic field due to a small magnetic dipole of dipole moment 'M' at a distance 'r' from the centre along the axis of the dipole is given by
Answer: μ 0 /4π * 2M/r 3

Question 28: A coil of an ac generator, having 100 turns and area 0.1 m 2 each, rotates at half a rotation per second in a magnetic field of 0.02 T. The maximum emf generated in the coil is
Answer: 0.63 V

Question 29: Two long solenoids of radii r 1 and r 2 (>r 1 ) and number of turns per unit length n 1 and n 2 respectively are co-axially wrapped one over the other. The ratio of self-inductance of inner solenoid to their mutual inductance is
Answer: n 1 /n 2

Question 30: A diamagnetic substance is brought, one by one, near the north pole and the south pole of a bar magnet. It is
Answer: repelled by the north pole as well as the south pole.

Question 31: A battery of e.m.f. 12 V and internal resistance 0.5 Ω is connected to a 9.5 Ω resistor through a key. The ratio of potential difference between the two terminals of the battery, when the key is open to that when the key is closed, is
Answer: 1.05

Question 32: Two identical point charges are placed at the two vertices A and B of an equilateral triangle of side l . The magnitude of the electric field at the third vertex P is E. If a hollow conducting sphere of radius (1/4) is placed at P, the magnitude of the electric field at point P now becomes
Answer: Zero

Question 33: An alternating current is given by I = I 0 cos (100π)t. The least time the current takes to decrease from its maximum value to zero will be:
Answer: (1/200)s

Question 34: Two horizontal plates, separated by 1 cm, are arranged one above the other. A particle of mass 5 mg and charge 2 nC is released in air between the plates. The potential difference that should be applied to the plates so that the particle remains suspended between them, is:
Answer: 250 V

The CBSE Physics Class 12 Answer Key 2025 available above is created by considering the reviews shared by the subject experts. Any discrepancies in the CBSE Class 12 Physics Answer Key 2025 are deeply regretted. Students are advised to refer to this unofficial answer key only for their reference.

Also Check | CBSE 12 Physics Exam Analysis 2025