CSIR NET Physical Science Most Repeated Questions 2026 with Topic Analysis

CSIR NET Physical Science Most Repeated Questions: The National Testing Agency (NTA) will conduct the CSIR NET 2026 Physical Science examination on July 17 and July 18, 2026, in Computer-Based Test (CBT) mode. As the examination approaches, candidates often look for the CSIR NET Physical Science Most Repeated Questions to understand which concepts have appeared consistently over recent sessions.

Based on approximately 450 questions from six papers conducted between June 2023 and December 2025, this analysis highlights the most frequently asked PYQs, repeated question patterns, unit-wise important concepts, and practical preparation strategies to help candidates revise more effectively. 

CSIR NET Physical Science Most Repeated Questions: Paper Pattern Analysis

The CSIR NET Physical Science Repeated Question Patterns observed across six previous papers show that several concepts are tested repeatedly with different numerical values or physical systems. 

Instead of memorising individual questions, candidates should understand the common solving methods used for these recurring problems. 

General Aptitude continues to contribute around one-fourth of the paper. Since many questions are based on logical reasoning, arithmetic, probability, and data interpretation, practising previous year questions can improve both speed and accuracy. 

CSIR NET Physical Science Frequently Asked Questions (Unit-wise) 

The following CSIR NET Physical Science Frequently Asked Questions are based on concepts that have appeared repeatedly in previous years. These questions cover the core principles that candidates should revise before the examination. 

Unit 1: Mathematical Physics

Q. How do you locate a branch point vs a pole in a complex function?
Answer: A branch point arises from a non-integer power or root (for example, √(z−z₀)). A pole arises from a factor in the denominator raised to an integer power. Papers repeatedly test this distinction with functions like √[(z²−5z+6)/(z²+2z+1)].

Q. What is the application of the Cayley-Hamilton theorem?
Answer: Every square matrix satisfies its own characteristic equation. It is used to reduce higher powers of a matrix (A³, A⁴, etc.) to a combination of I, A, and A². It appears almost every paper as "find (α, β) such that A³ + αA² + βA + ...".

Unit 2: Classical Mechanics

Q. What is the standard method to go from H(x,p) to L?
Answer: Solve ẋ = ∂H/∂p for p(x,ẋ), then substitute into L = pẋ − H.

Q. For a central potential V(r) = βrᵏ, what is the condition for a stable circular orbit?
Answer: The effective potential's second derivative must be positive at r₀, leading to the condition k > −3 for stability in the standard treatment.

Q. How does Noether's theorem relate symmetry to conserved quantity?
Answer: A continuous symmetry of L (for example, rotation x→x+εy, y→y+εx) implies a conserved combination of canonical momenta (such as yPₓ − xPᵧ or similar), directly from ∂L/∂ε = 0.

Unit 3: Electromagnetic Theory

Q. What is the field at the centre of a spherical cavity scooped from a uniformly charged sphere?
Answer: Apply the superposition principle by treating it as a full sphere plus a sphere of opposite (−ρ) charge density at the cavity. The field is uniform inside the cavity and is given by (ρ/3ε₀) × (vector from cavity centre to sphere centre).

Q. What is the field inside a dielectric cavity given external field E₀ and polarization P?
Answer: For a spherical cavity, Ecenter = E₀ + P/(3ε₀).

Q. What is the direction and physical meaning of the Poynting vector?
Answer: S = (1/μ₀)(E×B). It points in the direction of energy flow and is repeatedly tested for radiating charges, current-carrying wires, and reflected or incident wave superpositions.

Unit 4: Quantum Mechanics

Q. What is the probability of remaining in the ground state after a sudden change in oscillator frequency (ω→ω')?
Answer: P = |⟨ψ₀'|ψ₀⟩|². Compute the overlap integral of the old and new ground-state Gaussians.

Q. For two identical fermions, what symmetry must the total wavefunction have?
Answer: It must be antisymmetric under particle exchange. If the spin part is symmetric (triplet), the spatial part must be antisymmetric, and vice versa (singlet with symmetric spatial part).

Q. What is the standard identity for ladder operators in the quantum harmonic oscillator?
Answer: â|n⟩ = √n|n−1⟩ and â†|n⟩ = √(n+1)|n+1⟩. The operators x and p are expressed using â and ↠to evaluate expectation values and matrix elements.

Unit 5: Thermodynamics & Statistical Mechanics

Q. How do you obtain the temperature dependence of Cv from a bosonic dispersion ε(k) ∝ kˢ in d dimensions?
Answer: Cv ∝ T^(d/s). This reproduces T³ (phonons, s=1, d=3), T³ᐟ² (magnons, s=2, d=3), T² (s=1, d=2), and similar cases.

Q. What is the pressure ordering for classical, Fermi, and Bose ideal gases at the same temperature and number density?
Answer: PFermi > Pclassical > PBose.

Q. What is the entropy of a system with two energy levels (0, doubly degenerate ε) for large N?
Answer: Use Stirling's approximation on the multiplicity Ω(N, Nε). This gives S = kB[N ln N − N − (U/ε)ln(U/ε) + correction term], a standard large-N combinatorial expansion.

Unit 6: Electronics & Experimental Methods

Q. What is the output waveform of an ideal op-amp integrator with sinusoidal input?
Answer: The output is inverted and phase shifted by 90°, proportional to −(1/RC)∫Vin dt. For sinusoidal input, the output is a cosine (or negative cosine) of the same frequency, scaled by 1/(RC·ω).

Q. What is the standard error-propagation formula for a quantity like efficiency e = f(V, I, m, h, t)?
Answer: The fractional error is (δe/e) = √[Σ(∂lnf/∂xᵢ · δxᵢ)²]. Independent random errors are added in quadrature.

Q. Why do the two configurations differ in Four-probe or van der Pauw resistance measurement?
Answer: Contact and lead resistances contribute differently depending on the current and voltage terminal choice. The true channel resistance is obtained by comparing configurations A and B.

Unit 7: Atomic & Molecular Physics

Q. How does a spectral line split under a weak magnetic field (normal Zeeman effect)?
Answer: It splits into three components (ΔmJ = 0, ±1) with spacing μBB in energy. The magnetic moment can be determined from the observed splitting Δλ.

Q. How is bond length extracted from rotational-vibrational spectral lines (P and R branches)?
Answer: Determine the rotational constant B = ħ²/(2I) = ħ²/(2μr₀²) from the spacing of adjacent rotational lines, then calculate the equilibrium bond length r₀.

Q. What does Doppler broadening of a spectral line depend on?
Answer: The full Doppler width is proportional to (λ/c)·√(2kBT ln2 / m). It depends on temperature and atomic mass.

Unit 8: Condensed Matter Physics

Q. What is the standard result for phonon density of states in 1D from E = A|sin(ka)|?
Answer: g(E) ∝ 1/√(A² − E²). It is derived from dE/dk by inverting the density of states. Van Hove singularities appear at the band edges.

Q. What distinguishes Type I and Type II superconductors on an M-H plot?
Answer: Type I shows complete Meissner expulsion up to a single critical field Hc, followed by an abrupt transition. Type II shows a mixed or vortex state between Hc1 and Hc2 with a gradual decrease in magnetization.

Q. How can BCC and FCC lattices be identified using a lattice-point parity condition?
Answer: Lattice points with nx + ny + nz = odd integers form a BCC-type sublattice pattern, while nx + ny + nz = even integers form an FCC-type pattern.

Unit 9: Nuclear & Particle Physics

Q. What is the Q-value of alpha decay from atomic masses?
Answer: Q = [m(parent) − m(daughter) − m(⁴He)]·c². A positive Q-value indicates that the decay is energetically allowed. Always verify the sign convention.

Q. What determines the selection rule for nuclear gamma transition multipolarity?
Answer: It is determined by the change in spin (ΔJ) and parity change between the initial and final states. The lowest allowed multipolarity dominates the emitted radiation.

Q. How is uranium dating performed using two isotopes with different half-lives?
Answer: Set up N(t) = N₀e^(−t/τ) for both ²³⁵U and ²³⁸U, assuming equal initial abundance. Use their current ratio and respective mean lifetimes to determine the age.

CSIR NET Physical Science Important PYQs for Revision 

The following CSIR NET Physical Science Important PYQs represent concepts that have appeared repeatedly across multiple examination sessions. Practising these areas helps candidates strengthen conceptual understanding and improve problem-solving speed. 

• Complex analysis and residue theorem

• Matrix algebra

• Canonical transformations

• Harmonic oscillator

• Spin algebra

• Density of states calculations

• Partition function problems

• Boundary value problems

• Error propagation

• Spectroscopy

• Binding energy calculations

• Lattice geometry

Practising these CSIR NET Physical Science Important PYQs regularly helps improve conceptual clarity, calculation speed, and examination accuracy. 

CSIR NET Physical Science Repeated Question Patterns: Preparation Strategy 

Preparing repeated topics can improve overall performance because many question types follow familiar methods.

A practical preparation strategy includes:

• Complete General Aptitude practice every week.

• Revise Quantum Mechanics and Statistical Physics regularly.

• Practice Hamiltonian and Lagrangian conversions until the method becomes familiar.

• Solve numerical questions on density of states and specific heat.

• Revise op-amp circuits and common electronics configurations.

• Practice spectroscopy and Zeeman effect formulas.

• Solve binding energy and decay problems without using shortcuts.

• Attempt previous year papers under timed conditions.

Consistent revision of these recurring topics helps build confidence before the examination.

The analysis of six recent CSIR NET Physical Science papers shows that several concepts are repeatedly tested with different numerical values or applications. Instead of memorising individual questions, candidates should understand the solving approach behind these repeated question patterns. Regular practice of previous year questions, combined with consistent revision of high-weightage units, can strengthen conceptual understanding and improve performance in the CSIR NET Physical Science examination.