The morning paper of 22 January 2026, the third shift of Session 1. Below is the Physics section question by question, the chapter split, where the hundred marks sat, how tough it was, and the official answer key from NTA.
The shift
| Date | 22 January 2026 |
|---|---|
| Shift | Shift 1 — 9:00 AM to 12:00 PM IST |
| Paper | Paper 1 (B.E./B.Tech) |
| Whole paper | 75 questions, 300 marks, 180 minutes |
| Physics | Q26 to Q50 — Section A 20 MCQ (80 marks), Section B 5 numeric (20 marks) |
| Marking | +4 right, −1 wrong, nothing for a blank |
Physics, question by question
| Q | What it asked | Chapter |
|---|---|---|
| 26 | Metre bridge — two resistances from the null point before and after a shunt | Current Electricity |
| 27 | Six point charges set 60° apart on a circle — field at the centre | Electric Charges and Fields |
| 28 | Two rods of different materials joined — junction temperatures | Thermal Properties of Matter |
| 29 | Convex and concave lens, in contact and then with a gap — ratio of magnifications | Ray Optics |
| 30 | Two statements on fluid pressure and on surface tension | Mechanical Properties of Fluids |
| 31 | Equilateral prism — angle of refraction when the emergent ray grazes out | Ray Optics |
| 32 | Three coils on a common axis — which motion gives a clockwise induced current | Electromagnetic Induction |
| 33 | Four unequal masses at the corners of a square — force ratio after a swap | Gravitation |
| 34 | Match four quantities to their dimensional formulae | Units and Measurements |
| 35 | Potential at the origin from a field that grows with x and y | Electrostatic Potential and Capacitance |
| 36 | Rod sliding down a vertical loop in a field — terminal speed | Electromagnetic Induction |
| 37 | Alpha particle on a Z = 79 target — estimated nuclear diameter | Atoms |
| 38 | Two touching solid spheres — moment of inertia about the common tangent | Rotational Motion |
| 39 | Volume up eight times, temperature down to a quarter, no heat exchanged — name the gas | Thermodynamics |
| 40 | Closed tube of gas spun about one end — pressure at the two ends | Kinetic Theory of Gases |
| 41 | Escape velocity from a planet whose density and radius are a tenth | Gravitation |
| 42 | Projectile thrown at 60°, moving at 45° when its speed is 20 m/s — the launch speed | Motion in a Plane |
| 43 | Least photon frequency that splits a nucleus into four alpha particles | Nuclei |
| 44 | Which set of four inputs makes the LED glow | Semiconductor Electronics |
| 45 | Charged pendulum bob in a horizontal electric field — tension at equilibrium | Oscillations |
| 46 | numeric Two discs of the same material with equal moment of inertia — thickness ratio | Rotational Motion |
| 47 | numeric Parallel beam onto one curved glass surface — where it converges | Ray Optics |
| 48 | numeric Energy density in a coil when the current reaches 1/e of its final value | Electromagnetic Induction |
| 49 | numeric Two loudspeakers — frequency from the count of maxima and minima | Waves |
| 50 | numeric Dielectric constant of a medium from the wave equation | Electromagnetic Waves |
Chapter by chapter
| Chapter | Questions | Marks |
|---|---|---|
| Electromagnetic Induction | 3 | 12 |
| Ray Optics | 3 | 12 |
| Gravitation | 2 | 8 |
| Rotational Motion | 2 | 8 |
| Atoms | 1 | 4 |
| Current Electricity | 1 | 4 |
| Electric Charges and Fields | 1 | 4 |
| Electromagnetic Waves | 1 | 4 |
| Electrostatic Potential and Capacitance | 1 | 4 |
| Kinetic Theory of Gases | 1 | 4 |
| Mechanical Properties of Fluids | 1 | 4 |
| Motion in a Plane | 1 | 4 |
| Nuclei | 1 | 4 |
| Oscillations | 1 | 4 |
| Semiconductor Electronics | 1 | 4 |
| Thermal Properties of Matter | 1 | 4 |
| Thermodynamics | 1 | 4 |
| Units and Measurements | 1 | 4 |
| Waves | 1 | 4 |
All 19 shifts of JEE Main 2026, counted together chapter by chapter: JEE Main Physics important chapters.
Nineteen chapters again. Ray Optics got three questions here, which it did not in any other 2026 shift, and all three were different in kind: a lens combination, a prism at the critical angle, and refraction at a single curved surface. Electromagnetic Induction also took three, worth 12 marks.
Where the 100 marks sat
| Part of Physics | Questions | Marks | Share |
|---|---|---|---|
| Electrodynamics | 7 | 28 | 28% |
| Optics and Waves | 5 | 20 | 20% |
| Mechanics | 5 | 20 | 20% |
| Properties of Matter and Heat | 4 | 16 | 16% |
| Modern Physics and Electronics | 3 | 12 | 12% |
| Units, Dimensions and Measurement | 1 | 4 | 4% |
The one shift of the year where optics and waves tied with mechanics at 20 marks each. Units got only one question, the lightest it was treated anywhere in 2026 — a single match-the-dimensions question for 4 marks.
How tough it was
| Level | Questions | Share | Which ones |
|---|---|---|---|
| Straight recall or one step | 6 | 24% | 30, 34, 39, 42, 45, 50 |
| Two or three steps | 13 | 52% | 26, 31, 32, 35, 36, 37, 38, 40, 41, 43, 44, 46, 47 |
| Long or awkward | 6 | 24% | 27, 28, 29, 33, 48, 49 |
The lens pair, first in contact and then with a gap opened between them, had to be solved twice over, and the six charges on a circle needed every component resolved. Those two alone could swallow ten minutes. Against them, the dimensional matching and the dielectric constant were both single lines.
All 25 Physics questions, solved
Q1 · Current Electricity · on the pattern of Q26
A metre bridge carries two resistances R1 and R2 in its two gaps and balances at 40 cm from the end on the R1 side. When a 16 Ω resistance is joined in parallel with R2, the balance point moves to 50 cm. The values of R1 and R2 are ______.
Answer R2 = 8 Ω, R1 = 16/3 Ω
Where it goes wrong Cancelling R2 carelessly in the second equation. R2 appears on both sides, so divide it out before clearing the fraction, not after.
Q2 · Electric Charges and Fields · on the pattern of Q27
Six point charges are fixed on a circle of radius R, 60° apart. Going round the circle they are +q, +q, +q, −q, −q, −q, so that the three positive ones sit together on one half and the three negative ones on the other. The magnitude of the net electric field at the centre is ______.
Answer q / πε0R2
Where it goes wrong Expecting the six to cancel because there are three of each. They would cancel only if the pairs sat opposite each other; here each positive faces a negative, so the fields add instead.
Q3 · Thermal Properties of Matter · on the pattern of Q28
Two rods x and y of the same length and the same cross-section are joined end to end. The free end of x is held at 100 °C and the free end of y at 20 °C. The thermal conductivity of x is three times that of y. In the steady state the junction temperature is ______ °C.
Answer 80 °C
Where it goes wrong Taking the average, 60 °C. That is right only when the two conductivities are equal.
Q4 · Ray Optics · on the pattern of Q29
A convex lens of focal length 10 cm and a concave lens of focal length 20 cm are held in contact with no gap between them. An object is placed 30 cm in front of the convex lens. The magnification of the combination is ______.
Answer −2 (twice the size, inverted)
Where it goes wrong Adding the focal lengths instead of the powers. It is 1/f that adds, not f.
Q5 · Mechanical Properties of Fluids · on the pattern of Q30
Two statements. Statement I: the pressure of a fluid acts only on a solid surface in contact with it, and does not exist everywhere inside a still fluid. Statement II: the extra potential energy of the molecules at a liquid surface, compared with those inside, is what gives rise to surface tension. Which is true?
Answer Statement I is false, Statement II is true
Where it goes wrong Marking both false because the first half sounds half-right. Pressure at a point is defined everywhere in a fluid, not only at a wall.
Q6 · Ray Optics · on the pattern of Q31
An equilateral prism is made of a material of refractive index 1.5. Light falls on one face and the emergent ray is found to graze along the other face. The angle of refraction at the first face is about ______.
Answer about 18°
Where it goes wrong Using 30° for both angles of refraction. That is the symmetric, minimum-deviation path, not this one.
Q7 · Electromagnetic Induction · on the pattern of Q32
A coil of 100 turns and area 4 × 10−3 m2 lies with its plane at right angles to a magnetic field, which falls steadily from 0.5 T to 0.1 T in 0.2 s. The induced emf in the coil is ______ V.
Answer 0.8 V
Where it goes wrong Leaving out the number of turns. Each turn adds its own emf, so the 100 multiplies.
Q8 · Gravitation · on the pattern of Q33
Masses M, 2M, 3M and 4M are placed at the corners A, B, C and D of a square, taken in order. The net gravitational force at the centre is F1. The masses at C and D are then interchanged and the net force becomes F2. The ratio F1/F2 is ______.
Answer 2/√5, about 0.89
Where it goes wrong Adding the four forces as plain numbers. They point in four different directions, so the two diagonals must be handled separately and then combined.
Q9 · Units and Dimensions · on the pattern of Q34
Match each quantity with its dimensional formula: (A) spring constant, (B) thermal conductivity, (C) Boltzmann constant, (D) inductive reactance. The formulae on offer are ML2T−2K−1, ML0T−2, ML2T−3A−2 and MLT−3K−1.
Answer A → ML0T−2, B → MLT−3K−1, C → ML2T−2K−1, D → ML2T−3A−2
Where it goes wrong Mixing up the two that carry a K. Boltzmann constant is energy per kelvin, conductivity is power per length per kelvin — the extra T−1 and the L tell them apart.
Q10 · Electrostatic Potential · on the pattern of Q35
In a certain region the electric field is E = Axĥ + Byĵ, with A = 10 V/m2 and B = 5 V/m2. The potential at the point (10, 20) is 500 V. The potential at the origin is ______ V.
Answer 2000 V
Where it goes wrong Treating the field as uniform and using V = Ed. The field grows with position, so the integral brings in the square of the coordinate.
Q11 · Electromagnetic Induction · on the pattern of Q36
A vertical rectangular loop of total resistance R has two long vertical rails a distance l apart, in a uniform field B at right angles to the plane of the loop. A rod of mass m, longer than l, slides down the rails from rest without friction. Its terminal speed is ______.
Answer mgR / B2l2
Where it goes wrong Using the rod’s full length L. The part sticking out beyond the rails carries no current, so it contributes nothing.
Q12 · Atoms · on the pattern of Q37
A 7.9 MeV alpha particle is fired head on at a target of atomic number 79. From this the estimated diameter of the target nucleus is about ______ m. (1/4πε0 = 9 × 109 N·m2/C2, e = 1.6 × 10−19 C.)
Answer about 5.76 × 10−14 m
Where it goes wrong Stopping at the closest approach and calling it the diameter. It is the radius; the question asks for the diameter.
Q13 · Rotational Motion · on the pattern of Q38
A solid sphere of mass 5 kg and radius 10 cm touches a second solid sphere of mass 10 kg and radius 20 cm. The moment of inertia of the pair about the common tangent at the point of contact is ______ kg·m2.
Answer 0.63 kg·m2
Where it goes wrong Using the distance between the centres, 0.3 m, for one of the spheres. Each sphere’s own radius is its distance from the tangent.
Q14 · Thermodynamics · on the pattern of Q39
The volume of an ideal gas becomes 8 times its starting value while its temperature falls to one quarter, and no heat is exchanged with the surroundings. Of carbon dioxide, ammonia, helium and oxygen, the gas is ______.
Answer Helium
Where it goes wrong Using PVγ = constant when the data give temperature and volume. The TV form saves a step; both give the same γ.
Q15 · Kinetic Theory of Gases · on the pattern of Q40
A tube AB of length l, closed at both ends, holds 1 mole of an ideal gas of molar mass M. It is spun in a horizontal plane with constant angular velocity ω about a vertical axis through the end A. The temperature is the same everywhere. The relation between the pressures at the two ends is ______.
Answer PB = PA exp(Mω2l2/2RT)
Where it goes wrong Leaving out the factor of 2 by treating ω2r as constant. The integral of r dr brings l2/2, not l2.
Q16 · Gravitation · on the pattern of Q41
The escape velocity from a spherical planet A is 10 km/s. Planet B has a density and a radius each equal to 10% of those of A. The escape velocity from B is ______ m/s.
Answer 100√10 m/s, about 316 m/s
Where it goes wrong Assuming the mass is also a tenth. The mass goes as ρR3, so it drops to one ten-thousandth here.
Q17 · Motion in a Plane · on the pattern of Q42
A projectile is thrown at 60° above the horizontal. At the instant its direction of motion makes 45° with the horizontal, its speed is 20 m/s. The speed with which it was thrown is ______ m/s.
Answer 20√2 m/s, about 28.3 m/s
Where it goes wrong Trying to use the vertical component, which does change, or using energy, which needs the height. The constant horizontal component is the one line that settles it.
Q18 · Nuclei · on the pattern of Q43
The least photon frequency that can break a nucleus of mass 15.348 u into four alpha particles is ______ kHz. (mass of a helium nucleus = 4.002 u, 1 u = 1.66 × 10−27 kg, h = 6.6 × 10−34 J·s, c = 3 × 108 m/s.)
Answer 14.94 × 1019 kHz
Where it goes wrong Leaving the answer in hertz when the question asks for kilohertz. Divide by 103 at the end.
Q19 · Semiconductor Electronics · on the pattern of Q44
Inputs A and B feed a NAND gate. Its output and a third input C feed an AND gate, whose output drives an LED. The LED glows for which values of A, B and C?
Answer C = 1, with A and B not both 1 — for example A = 0, B = 1, C = 1
Where it goes wrong Reading the NAND as an AND and looking for A = B = 1. The NAND inverts, so its 1 means its inputs were not both 1.
Q20 · Oscillations · on the pattern of Q45
A simple pendulum has a bob of mass m carrying charge q, on a string of negligible mass. A uniform horizontal electric field E is switched on. The tension in the string once the pendulum settles at its new equilibrium is ______.
Answer √(m2g2 + q2E2)
Where it goes wrong Adding or subtracting the two forces as plain numbers. They are perpendicular, so it is the Pythagorean sum.
Q21 · Rotational Motion · numeric · on the pattern of Q46
A circular disc has radius R1 and thickness T1. A second disc of the same material has radius R2 and thickness T2. Their moments of inertia about their own axes are equal, and R1/R2 = 1/2. If T1/T2 = α, the value of α is ______.
Answer 16
Where it goes wrong Using R2 instead of R4. The radius enters once through the formula and twice more through the mass.
Q22 · Ray Optics · numeric · on the pattern of Q47
A parallel beam of light travelling in air falls on a convex spherical glass surface of radius of curvature 50 cm. The refractive index of the glass is 1.5. The rays meet at a point x cm from the centre of curvature of the surface. The value of x is ______ cm.
Answer 100 cm
Where it goes wrong Giving 150 cm, the distance from the surface. The question measures from the centre of curvature.
Q23 · Electromagnetic Induction · numeric · on the pattern of Q48
A long solenoid 50 cm long has 1000 turns and carries a current of 2 A. The energy density of the magnetic field inside it is ______ J/m3. (μ0 = 4π × 10−7 T·m/A.)
Answer 3.2π J/m3, about 10.1 J/m3
Where it goes wrong Using n = 1000 instead of 2000. The turns per metre is the count divided by the length in metres, and 50 cm is half a metre.
Q24 · Waves · numeric · on the pattern of Q49
Two loudspeakers 10 m apart are fed the same audio signal. A recorder starts at the midpoint of the line joining them and is moved 4 m along that line towards one speaker. Over the move the signal passes through 10 complete cycles of maxima and minima. The frequency of the signal is ______ Hz. (Speed of sound = 324 m/s.)
Answer 405 Hz
Where it goes wrong Taking the path difference as x instead of 2x. Both distances change, and in opposite senses, so the difference changes twice as fast as the recorder moves.
Q25 · Electromagnetic Waves · numeric · on the pattern of Q50
The electric field of a plane electromagnetic wave in an unknown non-magnetic medium is Ey = 20 sin(3 × 106x − 4.5 × 1014t) V/m, in SI units. The dielectric constant of the medium is ______. (c = 3 × 108 m/s.)
Answer 4
Where it goes wrong Giving 2, the refractive index. The dielectric constant is its square, and it is only the square for a non-magnetic medium.
The official answer key
NTA did not publish the Session 1 question papers. They were shown only inside each candidate’s own login during the answer key challenge window in February 2026, and that window is closed. The one official file for this shift is the final answer key, which covers all ten January shifts. The other January 2026 dates were 21, 23, 24 and 28 January, two shifts on each.
All shifts, date by date: JEE Main Previous Years Papers.
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