The afternoon paper of 24 January 2026, the eighth 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 2 — 3:00 PM to 6:00 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 | Two coaxial loops carrying I and 4I — the field at a point on the axis | Moving Charges and Magnetism |
| 27 | Flexible chain hanging at 30° at its supports — tension at the lowest point | Laws of Motion |
| 28 | Detector sphere whose volume is made eight times bigger — the intensity | Waves |
| 29 | Fifth harmonic of a closed pipe in unison with the first of an open pipe | Waves |
| 30 | Vertical circle where the thread goes slack at 30° — speed at the bottom | Laws of Motion |
| 31 | Three ways of filling a capacitor with two dielectrics — ranking them | Electrostatic Potential and Capacitance |
| 32 | Object and its three times magnified real image 40 cm apart — the focal length | Ray Optics |
| 33 | Intensity on the screen directly in front of one of the two slits | Wave Optics |
| 34 | Rod pivoted a third of the way up, falling flat — angular velocity on landing | Rotational Motion |
| 35 | Vernier callipers with 50 divisions matching 48 — the least count | Units and Measurements |
| 36 | Correct truth table for the given logic circuit | Semiconductor Electronics |
| 37 | Heat involved as an ideal gas goes from one state to another | Thermodynamics |
| 38 | Ammeter reading in the steady state of the given circuit | Current Electricity |
| 39 | Shunt needed to turn a galvanometer into a 5 mA ammeter | Moving Charges and Magnetism |
| 40 | Hexagon of wires with spokes to the centre — resistance across a diagonal | Current Electricity |
| 41 | Five sets of object and image distances for one lens — which reading is wrong | Ray Optics |
| 42 | Velocity against distance graph — the matching acceleration against distance graph | Motion in a Straight Line |
| 43 | Stopping potential at one wavelength and at twice it — the first wavelength | Dual Nature of Radiation and Matter |
| 44 | Cubical block floating in a denser liquid — depth of the submerged part | Mechanical Properties of Fluids |
| 45 | Two nuclear reactions with given energies — order of stability of He-3, He-4, He-5 | Nuclei |
| 46 | numeric Work done in blowing a soap bubble to twice its radius | Mechanical Properties of Fluids |
| 47 | numeric Point charge near the end of a uniformly charged rod — the force | Electric Charges and Fields |
| 48 | numeric Metre bridge null point shifted 10 cm by a parallel resistor | Current Electricity |
| 49 | numeric Small cylinder carved from a big one — ratio of their moments of inertia | Rotational Motion |
| 50 | numeric 300 J given to a gas at constant volume — the mass of the gas | Thermodynamics |
Chapter by chapter
| Chapter | Questions | Marks |
|---|---|---|
| Current Electricity | 3 | 12 |
| Laws of Motion | 2 | 8 |
| Mechanical Properties of Fluids | 2 | 8 |
| Moving Charges and Magnetism | 2 | 8 |
| Ray Optics | 2 | 8 |
| Rotational Motion | 2 | 8 |
| Thermodynamics | 2 | 8 |
| Waves | 2 | 8 |
| Dual Nature of Radiation and Matter | 1 | 4 |
| Electric Charges and Fields | 1 | 4 |
| Electrostatic Potential and Capacitance | 1 | 4 |
| Motion in a Straight Line | 1 | 4 |
| Nuclei | 1 | 4 |
| Semiconductor Electronics | 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.
Only sixteen chapters here, the tightest of any January shift, and eight of them took two or three questions. Current Electricity alone carried 12 marks across three questions — a steady-state circuit, a hexagon network and a metre bridge. A student who had drilled circuits was handsomely paid in this shift.
Where the 100 marks sat
| Part of Physics | Questions | Marks | Share |
|---|---|---|---|
| Electrodynamics | 7 | 28 | 28% |
| Mechanics | 5 | 20 | 20% |
| Optics and Waves | 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 same 28 / 20 / 20 / 16 / 12 / 4 that most 2026 shifts settled into. Nothing surprising in the balance; the difficulty was all in the individual questions.
How tough it was
| Level | Questions | Share | Which ones |
|---|---|---|---|
| Straight recall or one step | 7 | 28% | 28, 32, 35, 38, 39, 44, 45 |
| Two or three steps | 12 | 48% | 26, 27, 29, 33, 36, 37, 41, 42, 43, 46, 48, 50 |
| Long or awkward | 6 | 24% | 30, 31, 34, 40, 47, 49 |
The hexagon with spokes to its centre is a classic that cannot be done by inspection — it needs node equations, and the answer 4r/5 is not one anybody guesses. The rod pivoted a third of the way up is almost as awkward, because the moment of inertia and the drop of the centre of mass both have to be worked out about a pivot that is at neither the end nor the middle.
All 25 Physics questions, solved
Q1 · Moving Charges and Magnetism · on the pattern of Q26
Two circular loops of radii r and 2r lie in the same plane with the same centre. They carry currents I and 4I in opposite senses. The magnetic field at the common centre is ______.
Answer μ0I/2r, in the sense of the larger loop
Where it goes wrong Adding the two because the larger loop carries more current. The senses are opposite, so they subtract whatever their sizes.
Q2 · Laws of Motion · on the pattern of Q27
A flexible chain of mass m hangs between two fixed points at the same level. At each support the chain makes 30° with the horizontal. The tension in the chain at its lowest point is ______.
Answer √3mg/2
Where it goes wrong Using the whole mass m for one half. Each half carries only half the weight, which is the whole reason for cutting it in two.
Q3 · Waves · on the pattern of Q28
A point source sits at the centre of a spherical detector. If the volume enclosed by the detector is made 8 times bigger, the intensity at its surface ______.
Answer falls to one quarter
Where it goes wrong Dividing the intensity by 8, as though it followed the volume. It follows the area, and the area is the two-thirds power of the volume.
Q4 · Waves · on the pattern of Q29
The fifth harmonic of a closed organ pipe is in unison with the first harmonic of an open pipe. The ratio of the length of the closed pipe to that of the open pipe is 5/x. The value of x is ______.
Answer 2
Where it goes wrong Using v/2L for the closed pipe. A closed pipe has an antinode at one end and a node at the other, so its fundamental wavelength is 4L, not 2L.
Q5 · Laws of Motion · on the pattern of Q30
A particle on a thread of length r is moving in a vertical circle. The tension in the thread falls to zero when the thread is 30° above the horizontal through the centre. The speed of the particle at the lowest point A of the circle is ______.
Answer √(7gr/2)
Where it goes wrong Measuring the 30° from the vertical, or forgetting that the point is above the centre so its height is r plus r sin30°, not r sin30°.
Q6 · Capacitance · on the pattern of Q31
A parallel plate capacitor of plate area A and separation d is filled with dielectrics in three ways. A: the stronger dielectric k1 fills the whole gap. B: k1 covers half the area and k2 the other half, each over the full gap. C: k1 fills half the thickness and k2 the other half, each over the full area. With k1 > k2, rank the three capacitances.
Answer CA > CB > CC
Where it goes wrong Mixing up which split is series and which is parallel. Dividing by area gives parallel; stacking across the gap gives series.
Q7 · Ray Optics · on the pattern of Q32
A mirror forms a real image three times the size of the object, and the object and image are 40 cm apart. The focal length of the mirror is ______ cm.
Answer −15 cm
Where it goes wrong Adding the two distances to get 40. For a real image from a mirror the object and image are on the same side, so the gap is the difference, not the sum.
Q8 · Wave Optics · on the pattern of Q33
In a Young’s double slit experiment each slit on its own would give intensity I0 on the screen. The slits are 2 mm apart, the screen is 10 m away and the wavelength is 6000 Å. The intensity at the point on the screen directly in front of one of the slits is ______.
Answer I0
Where it goes wrong Expecting a bright fringe in front of a slit and answering 4I0. There is nothing special about that point; the numbers decide, and here they give a phase of 120°.
Q9 · Rotational Motion · on the pattern of Q34
A thin uniform rod of mass M and length L is pivoted at a point L/3 from its lower end. It is held vertical and allowed to fall until it lies horizontally on the table. Its angular velocity as it hits the table is ______.
Answer √(3g/L)
Where it goes wrong Using ML2/3, the value about an end. The pivot is a third of the way up, so the parallel axis theorem has to be applied from the centre.
Q10 · Units and Measurement · on the pattern of Q35
In a vernier callipers 50 vernier scale divisions coincide with 48 main scale divisions, and one main scale division is 0.05 mm. The least count is ______ mm.
Answer 0.002 mm
Where it goes wrong Dividing 0.05 by 50 and answering 0.001 mm. That is right only when 50 vernier divisions match 49 main ones.
Q11 · Semiconductor Electronics · on the pattern of Q36
Inputs A and B go to an OR gate and also to a NAND gate. The two outputs are then fed into an AND gate, whose output is Y. Write the truth table for Y.
Answer Y = 0, 1, 1, 0 for (A,B) = (0,0), (0,1), (1,0), (1,1) — an exclusive OR
Where it goes wrong Reading the NAND as an AND, which would give a plain OR instead. The inversion in the NAND is what knocks out the (1,1) row.
Q12 · Thermodynamics · on the pattern of Q37
10 mole of an ideal gas with CV = 21 J/K·mol is held at constant volume at 300 K. It is heated until its pressure rises from 20 Pa to 30 Pa. The heat supplied is ______ J.
Answer 31500 J
Where it goes wrong Using CP out of habit. At constant volume there is no expansion to pay for, so CV is the right one.
Q13 · Current Electricity · on the pattern of Q38
A battery, a resistor and a capacitor are joined in one series loop, with an ammeter of negligible resistance in the loop. The ammeter reading in the steady state is ______ A.
Answer zero
Where it goes wrong Working out V/R and giving that. That is the current at the first instant, when the capacitor is still empty.
Q14 · Moving Charges and Magnetism · on the pattern of Q39
A moving coil galvanometer of resistance 100 Ω gives a full scale deflection for 1 mA. The resistance needed to turn it into an ammeter reading 5 mA at full scale is ______ Ω.
Answer 25 Ω, connected in parallel
Where it goes wrong Connecting it in series, which is how a voltmeter is made. An ammeter must not add resistance to the circuit it measures, so the extra resistance goes alongside, not in line.
Q15 · Current Electricity · on the pattern of Q40
A regular hexagon is made of six wires, each of resistance r, and each corner is also joined to the centre by a wire of the same resistance r. Current enters at one corner and leaves at the opposite corner. The resistance between those two corners is ______.
Answer 4r/5
Where it goes wrong Trying to reduce it by series and parallel alone. The spokes to the centre make the network irreducible that way, and node equations are the only honest route.
Q16 · Ray Optics · on the pattern of Q41
Five people measure object and image distances with the same convex lens of power +5 D and record (u, v) in cm as (25, 96), (30, 62), (35, 37), (45, 35) and (50, 32). Whose reading is wrong?
Answer the third one, (35, 37)
Where it goes wrong Suspecting (25, 96) because the numbers look extreme. An object just outside the focus genuinely throws its image a long way off; the arithmetic is what decides.
Q17 · Motion in a Straight Line · on the pattern of Q42
The velocity of a particle grows in proportion to the distance covered, v = kx. The graph of acceleration against distance is ______.
Answer a straight line through the origin, a = k2x
Where it goes wrong Differentiating with respect to time and getting stuck. a = dv/dt needs x as a function of t; a = v dv/dx does the job in one line from the graph you already have.
Q18 · Dual Nature of Matter · on the pattern of Q43
Light of a certain wavelength falling on a metal surface gives a stopping potential of 3.2 V. With light of twice that wavelength the stopping potential drops to 0.7 V. The first wavelength is about ______ m. (h = 6.63 × 10−34 J·s, e = 1.6 × 10−19 C, c = 3 × 108 m/s.)
Answer about 2.5 × 10−7 m
Where it goes wrong Trying to find φ first. Subtracting the two equations kills it off straight away and leaves a single step.
Q19 · Mechanical Properties of Fluids · on the pattern of Q44
A cubical block of density 600 kg/m3 and height 8.0 cm floats in a liquid of density 900 kg/m3. The height of the submerged part is ______ cm.
Answer about 5.3 cm
Where it goes wrong Putting the ratio the other way up and getting 12 cm, which is taller than the block. A floating body is always less dense than the liquid, so the submerged fraction is always less than one.
Q20 · Nuclei · on the pattern of Q45
Two reactions: 3He + n → 4He releasing 20 MeV, and 4He + n → 5He absorbing 0.9 MeV. If X3, X4 and X5 are the stabilities of 3He, 4He and 5He, the correct order is ______.
Answer X4 > X5 > X3
Where it goes wrong Putting 5He at the bottom because its reaction absorbed energy. The two energies have to be compared with each other, not just read for their signs.
Q21 · Mechanical Properties of Fluids · numeric · on the pattern of Q46
A soap bubble of surface tension 0.04 N/m is blown to a radius of 7 cm. The work done in blowing it further to a radius of 14 cm is (15000 − x) μJ. The value of x is ______. (π = 22/7.)
Answer 216
Where it goes wrong Leaving out the factor of 2 for the two surfaces. A soap film has an inside and an outside; a liquid drop would have only one.
Q22 · Electric Charges and Fields · numeric · on the pattern of Q47
A point charge q = 1 μC sits on the line of a thin insulating rod, 2 cm from one end. The rod is 10 cm long and carries Q = 24 μC spread evenly along it. The force between the charge and the rod is ______ N. (1/4πε0 = 9 × 109 N·m2/C2.)
Answer 90 N
Where it goes wrong Treating the rod as a point charge at its centre, 7 cm away, which gives about 44 N. The near end is only 2 cm away and dominates, so the integral cannot be shortcut.
Q23 · Current Electricity · numeric · on the pattern of Q48
In a metre bridge, 2 Ω is in the left gap and 3 Ω in the right, and the null point is found at l cm from the left. When an unknown resistance x is joined in parallel with the 3 Ω, the null point moves 10 cm to the right. The value of x is ______ Ω.
Answer 6 Ω
Where it goes wrong Expecting x to be smaller than 3 Ω because the parallel combination drops to 2. A 6 Ω resistor across 3 Ω gives exactly 2 Ω; the parallel value only has to fall below 3, not the resistor itself.
Q24 · Rotational Motion · numeric · on the pattern of Q49
A uniform solid cylinder of length L and radius R has moment of inertia I1 about its own axis. A smaller coaxial cylinder of length L/2 and radius R/3 is carved out of it, and its moment of inertia about the same axis is I2. The ratio I1/I2 is ______.
Answer 162
Where it goes wrong Using R2 and forgetting that the mass also carries R2. Together they make the fourth power, which is where the big factor comes from.
Q25 · Thermodynamics · numeric · on the pattern of Q50
300 J of heat is given to oxygen, for which CP = (7/2)R, and its temperature rises from 20 °C to 50 °C at constant volume. The mass of the gas is about ______ g. (R = 8.314 J/mol·K, molar mass of oxygen = 32 g/mol.)
Answer about 15.4 g
Where it goes wrong Using the given CP directly. It is handed over only so that CV can be found from it, since the volume is fixed.
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. Shift 1 of the same day, 24 January 2026, is on its own page, and the other January dates are 21, 22, 23 and 28 January.
All shifts, date by date: JEE Main Previous Years Papers.
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