The morning paper of 24 January 2026, the seventh 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 | 24 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 | Ball thrown at 45°, peaks at 2 s and lands on a roof at 3 s — the roof height | Motion in a Plane |
| 27 | Potential varying as ar³ + b — the charge inside unit radius | Electrostatic Potential and Capacitance |
| 28 | Two electrons of different speeds in orbits of the same radius — the quantum numbers | Atoms |
| 29 | Prism at minimum deviation exactly meeting the critical angle — the prism angle | Ray Optics |
| 30 | Power factor of a series LCR circuit on a 220 V, 50 Hz supply | Alternating Current |
| 31 | Match each kind of electromagnetic wave to how it is produced | Electromagnetic Waves |
| 32 | Match magnetic induction, flux, permeability and inductance to their dimensions | Units and Measurements |
| 33 | Taut wire cooled further — the temperature that raises the tension to 1.4T | Mechanical Properties of Solids |
| 34 | Three concentric charged shells — the potential of each | Electrostatic Potential and Capacitance |
| 35 | Reflected and refracted rays at right angles — the angle of incidence | Wave Optics |
| 36 | Rise in the internal energy of water heated from 4 °C to 20 °C | Thermodynamics |
| 37 | Spring cut in the ratio 1 : 3 — force constant of the shorter piece | Oscillations |
| 38 | Two masses over a heavy pulley — the pulley’s rotational inertia | Rotational Motion |
| 39 | Two statements on binding energy per nucleon | Nuclei |
| 40 | Metre bridge null point shifted by a resistor in parallel — the unknown resistance | Current Electricity |
| 41 | Microscope of 10 cm tube length — magnification written as a power of 5 | Ray Optics |
| 42 | Voltmeter of finite resistance across one of two equal resistors — its reading | Current Electricity |
| 43 | Three masses moved to a larger triangle about the same centre — work done | Gravitation |
| 44 | Floating cylinder pushed down and let go — the period | Oscillations |
| 45 | Three charges in the xy plane — the resultant dipole moment about the origin | Electric Charges and Fields |
| 46 | numeric Sixty-four raindrops merging into one — the new terminal velocity | Mechanical Properties of Fluids |
| 47 | numeric Stacked blocks with friction everywhere — force to pull one out steadily | Laws of Motion |
| 48 | numeric Bar magnet turned from the most stable to the most unstable position | Magnetism and Matter |
| 49 | numeric Protective resistance for a Zener diode of given power rating | Semiconductor Electronics |
| 50 | numeric Gas in a closed cylinder heated to twice its temperature — the new pressure | Kinetic Theory of Gases |
Chapter by chapter
| Chapter | Questions | Marks |
|---|---|---|
| Current Electricity | 2 | 8 |
| Electrostatic Potential and Capacitance | 2 | 8 |
| Oscillations | 2 | 8 |
| Ray Optics | 2 | 8 |
| Alternating Current | 1 | 4 |
| Atoms | 1 | 4 |
| Electric Charges and Fields | 1 | 4 |
| Electromagnetic Waves | 1 | 4 |
| Gravitation | 1 | 4 |
| Kinetic Theory of Gases | 1 | 4 |
| Laws of Motion | 1 | 4 |
| Magnetism and Matter | 1 | 4 |
| Mechanical Properties of Fluids | 1 | 4 |
| Mechanical Properties of Solids | 1 | 4 |
| Motion in a Plane | 1 | 4 |
| Nuclei | 1 | 4 |
| Rotational Motion | 1 | 4 |
| Semiconductor Electronics | 1 | 4 |
| Thermodynamics | 1 | 4 |
| Units and Measurements | 1 | 4 |
| Wave Optics | 1 | 4 |
All 19 shifts of JEE Main 2026, counted together chapter by chapter: JEE Main Physics important chapters.
Twenty-one chapters again. Two of the three questions on electric potential and charge came close together, and the two on current electricity were both circuit-measurement questions — a metre bridge and a voltmeter that loads the circuit it is measuring. Those two are the pair of practical questions most students lose marks on.
Where the 100 marks sat
| Part of Physics | Questions | Marks | Share |
|---|---|---|---|
| Electrodynamics | 8 | 32 | 32% |
| Optics and Waves | 5 | 20 | 20% |
| Mechanics | 4 | 16 | 16% |
| Properties of Matter and Heat | 4 | 16 | 16% |
| Modern Physics and Electronics | 3 | 12 | 12% |
| Units, Dimensions and Measurement | 1 | 4 | 4% |
Electrodynamics 32, mechanics only 16, and units down to a single question. Of all the January shifts this one leaned hardest away from mechanics.
How tough it was
| Level | Questions | Share | Which ones |
|---|---|---|---|
| Straight recall or one step | 8 | 32% | 31, 32, 35, 37, 39, 41, 44, 50 |
| Two or three steps | 11 | 44% | 26, 27, 29, 30, 33, 34, 42, 45, 46, 48, 49 |
| Long or awkward | 6 | 24% | 28, 36, 38, 40, 43, 47 |
Two questions were unusual enough to be worth a second look even now. The water heated from 4 °C to 20 °C asks for the change in internal energy rather than the heat, so the tiny work done against the atmosphere has to be subtracted — and that work turns out to be less than a joule out of 268,800. And the two electrons in orbits of the same radius looks like a formula question but turns out to hinge on a single step: at equal radius, the speed is proportional to the quantum number itself.
All 25 Physics questions, solved
Q1 · Motion in a Plane · on the pattern of Q26
A ball is thrown into the air at 45° to the horizontal. It reaches its greatest height 2 s after launch and lands on the roof of a building 3 s after launch. The height H of the roof is ______ m. (g = 10 m/s2.)
Answer 15 m
Where it goes wrong Working out the maximum height, 20 m, and stopping there. The ball is on its way down at 3 s, so the roof is lower than the peak.
Q2 · Electrostatic Potential · on the pattern of Q27
In a charged spherical region the potential varies with distance as V = ar3 + b, where a and b are constants. The total charge inside a sphere of unit radius is απaε0. The value of α is ______.
Answer −12
Where it goes wrong Losing the minus sign from E = −dV/dr. For a potential that rises outward, the enclosed charge is negative.
Q3 · Atoms · on the pattern of Q28
Electrons in two different hydrogen-like atoms move at 3 × 105 m/s and 2.5 × 105 m/s, and the radii of the two orbits are nearly the same. A possible pair of quantum numbers is ______.
Answer n = 6 and n = 5
Where it goes wrong Using v ∝ 1/n straight away and looking for the smaller n with the larger speed. That holds at fixed Z, not at fixed radius, and here it is the radius that is fixed.
Q4 · Ray Optics · on the pattern of Q29
A prism of refractive index √2 stands in air. It is set at minimum deviation, and at that setting the ray inside it exactly meets the critical angle condition at the exit face. The prism angle is ______.
Answer 90°
Where it goes wrong Setting A = C instead of A/2 = C. The symmetry at minimum deviation is what halves it.
Q5 · Alternating Current · on the pattern of Q30
A series LCR circuit on a 220 V, 50 Hz supply has R = 8 Ω, and its inductive and capacitive reactances differ by 6 Ω. The power factor is α/10. The value of α is ______.
Answer 8
Where it goes wrong Adding XL and XC instead of subtracting. In series they oppose each other, so it is the difference that enters the impedance.
Q6 · Electromagnetic Waves · on the pattern of Q31
Match each wave to how it is produced: A. radio wave, B. microwave, C. infrared, D. X-ray. The mechanisms are: a magnetron valve; changes in the vibrational modes of atoms; inner shell electrons dropping to a lower level; rapid acceleration of electrons.
Answer A → rapid acceleration of electrons, B → magnetron valve, C → vibrational modes, D → inner shell electrons
Where it goes wrong Swapping infrared and microwave. Both are below visible light, but the vibrational-mode origin belongs to infrared; microwaves come from an electronic valve.
Q7 · Units and Dimensions · on the pattern of Q32
Match each quantity to its dimensional formula: A. magnetic induction, B. magnetic flux, C. magnetic permeability, D. self inductance. The formulae are MLT−2A−2, ML2T−2A−2, ML0T−2A−1 and ML2T−2A−1.
Answer A → ML0T−2A−1, B → ML2T−2A−1, C → MLT−2A−2, D → ML2T−2A−2
Where it goes wrong Confusing permeability with inductance, since both end in A−2. They differ by one power of length.
Q8 · Mechanical Properties of Solids · on the pattern of Q33
A brass wire is held taut between two rigid supports at 27 °C with no tension. It is cooled to −43 °C, which sets up a tension T. The temperature to which it must be cooled for the tension to become 1.4T is ______ °C.
Answer −71 °C
Where it goes wrong Multiplying −43 by 1.4. It is the temperature drop from 27 °C that scales, not the reading on the thermometer.
Q9 · Electrostatic Potential · on the pattern of Q34
Three concentric conducting spherical shells A, B and C of radii a, b and c, with c > b > a, carry charges q1, q2 and q3. Write down the potential of each shell.
Answer VA = k(q1/a + q2/b + q3/c), VB = k((q1+q2)/b + q3/c), VC = k(q1+q2+q3)/c
Where it goes wrong Using 1/a for q1 at shell B. Once a charge is inside the point you are at, its contribution is divided by the distance to the point, not by its own radius.
Q10 · Wave Optics · on the pattern of Q35
Unpolarised light travelling in a medium of refractive index √2 meets a boundary with a medium of refractive index √6. The angle of incidence at which the reflected and refracted rays come out at right angles to each other is ______.
Answer 60°
Where it goes wrong Putting the ratio upside down. The index of the second medium goes on top when light travels from the first into the second.
Q11 · Thermodynamics · on the pattern of Q36
The density of water is 1000 kg/m3 at 4 °C and 998 kg/m3 at 20 °C. The increase in internal energy of 4 kg of water when it is heated from 4 °C to 20 °C is ______ J. (Specific heat capacity of water = 4200 J/kg·°C, atmospheric pressure = 105 Pa.)
Answer 268799.2 J
Where it goes wrong Answering 268800 J. That is the heat, not the change in internal energy — and the point of giving the two densities is to make you find the work, however tiny it turns out to be.
Q12 · Oscillations · on the pattern of Q37
A spring of force constant 15 N/m is cut into two pieces whose lengths are in the ratio 1 : 3. The force constant of the shorter piece is ______ N/m.
Answer 60 N/m
Where it goes wrong Reading “ratio 1 : 3” as halves or thirds. One part in four and three parts in four is what it means.
Q13 · Rotational Motion · on the pattern of Q38
Masses of 400 g and 350 g hang from the ends of a light string over a heavy pulley of radius 2 cm. Released from rest, the heavier mass is seen to fall 81 cm in 9 s. The rotational inertia of the pulley is ______ kg·m2. (g = 9.8 m/s2.)
Answer 9.5 × 10−3 kg·m2
Where it goes wrong Forgetting to square the radius when converting I/r2 back to I. 2 cm squared is 4 × 10−4 m2, not 2 × 10−2.
Q14 · Nuclei · on the pattern of Q39
Two statements. Statement I: for all elements, the heavier the nucleus the greater its binding energy per nucleon. Statement II: for all elements, nuclei with a lower binding energy per nucleon tend to change into nuclei with a higher one. Which is true?
Answer Statement I is false, Statement II is true
Where it goes wrong Confusing total binding energy with binding energy per nucleon. The total does keep rising with mass; it is the per-nucleon figure that peaks and turns over.
Q15 · Current Electricity · on the pattern of Q40
A metre bridge has 2 Ω and 3 Ω in its two gaps and balances at some point of the wire XY. When an unknown resistor is joined in parallel with the 3 Ω, the balance point shifts 22.5 cm towards Y. The unknown resistance is ______ Ω.
Answer 2 Ω
Where it goes wrong Forgetting that the shunt must lower the right-hand resistance, which is why the balance moves away from the 2 Ω side. If the shift comes out the other way, the two gaps have been read the wrong way round.
Q16 · Ray Optics · on the pattern of Q41
A compound microscope of tube length 10 cm uses two convex lenses of focal lengths 2 cm and 5 cm. Its total magnification for normal adjustment is 5k. The value of k is ______. (Least distance of distinct vision = 25 cm.)
Answer 2
Where it goes wrong Putting the 5 cm lens as the objective, which gives (10/5)(25/2) = 25 as well — the same number by accident here, but the wrong reasoning, and it fails whenever the figures are less kind.
Q17 · Current Electricity · on the pattern of Q42
Two resistors of 100 Ω each are joined in series across a 9 V battery. A voltmeter of resistance 400 Ω is connected across one of them. The voltmeter reads ______ V.
Answer 4 V
Where it goes wrong Answering 4.5 V. That is the voltage before the meter was attached; a real voltmeter always reads a little low.
Q18 · Gravitation · on the pattern of Q43
Masses of 200 kg, 300 kg and 400 kg sit at the corners of an equilateral triangle of side 20 m. They are moved to the corners of a larger equilateral triangle of side 25 m with the same centre. The work done in the process is ______ J. (G = 6.7 × 10−11 N·m2/kg2.)
Answer 1.74 × 10−7 J
Where it goes wrong Forgetting that all three sides of an equilateral triangle are the same, so one denominator covers all three pairs. And the answer is positive: pulling masses apart against gravity needs work.
Q19 · Oscillations · on the pattern of Q44
A cylindrical block of mass M and cross-sectional area A floats with its axis vertical in a liquid of density ρ. It is pushed down a little and released, and it oscillates. The period of the oscillation is ______.
Answer 2π√(M/ρAg)
Where it goes wrong Putting ρAg on top instead of underneath. It plays the part of the spring constant, so it belongs in the denominator with M above it.
Q20 · Electric Charges and Fields · on the pattern of Q45
Charges +2q, +3q and −4q sit at (0, −3a), (2a, 0) and (−2a, 0) in the xy plane. The resultant dipole moment about the origin is ______.
Answer 2qa(7ĥ − 3ĵ)
Where it goes wrong Dropping one of the two minus signs in the third term. A negative charge at a negative coordinate gives a positive contribution.
Q21 · Mechanical Properties of Fluids · numeric · on the pattern of Q46
Sixty-four raindrops, each of radius 1 mm, are falling at a terminal velocity of 10 cm/s. They merge into one bigger drop. The terminal velocity of the bigger drop is ______ cm/s.
Answer 160 cm/s
Where it goes wrong Scaling by 64 or by 4 instead of by 16. The radius grows as the cube root of the number of drops, and the velocity then goes as its square.
Q22 · Laws of Motion · numeric · on the pattern of Q47
A block of 4 kg rests on top of a block of 6 kg, which rests on the ground. The coefficient of sliding friction is 0.5 between every pair of surfaces, including block and ground. The top block is held still by a string tied to a wall. The force needed to pull the lower block out at a constant speed is ______ N. (g = 10 m/s2.)
Answer 70 N
Where it goes wrong Using only 6 kg for the normal force at the ground. The ground holds up both blocks, so the full 10 kg presses on it.
Q23 · Magnetism and Matter · numeric · on the pattern of Q48
A short bar magnet set with its axis at 30° to an external field of 800 gauss feels a torque of 0.016 N·m. The work done in turning it from its most stable to its most unstable position is α × 10−3 J. The value of α is ______.
Answer 64
Where it goes wrong Answering mB instead of 2mB. The magnet is turned the whole way from aligned to anti-aligned, which costs twice as much.
Q24 · Semiconductor Electronics · numeric · on the pattern of Q49
A voltage regulating circuit uses a Zener diode of breakdown voltage 10 V, able to dissipate at most 0.4 W, run from a 15 V supply. The protective series resistance needed is about ______ Ω.
Answer about 125 Ω
Where it goes wrong Dividing the power by 15 V instead of 10 V. The diode’s own power is its own voltage times its own current, and its voltage is the breakdown value.
Q25 · Kinetic Theory of Gases · numeric · on the pattern of Q50
A fixed mass of gas in a closed cylinder is at 3.23 kPa and 50 °C. It is heated until its temperature is doubled. The new pressure is ______ Pa.
Answer 6460 Pa
Where it goes wrong Reading “double the temperature” as 100 °C. In gas problems a doubling is always of the kelvin value, and 100 °C is only 373 K.
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, 22, 23 and 28 January, two shifts on each.
All shifts, date by date: JEE Main Previous Years Papers.
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