The opening shift of JEE Main 2026, the first paper 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 | 21 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 | Satellite moved to a larger orbit — energy that has to be supplied | Gravitation |
| 27 | Alpha particle fired at a gold foil — closest it can get | Atoms |
| 28 | Electromagnetic wave — magnetic field from the electric field | Electromagnetic Waves |
| 29 | A changed Bernoulli equation — dimensions of its two constants | Units and Measurements |
| 30 | Force that grows with time — velocity and position later | Laws of Motion |
| 31 | Dielectric slab filling part of a capacitor — new capacitance | Electrostatic Potential and Capacitance |
| 32 | Sheet over one slit in a double slit set-up — its thickness | Wave Optics |
| 33 | Light carrying two frequencies — greatest kinetic energy of the electrons | Dual Nature of Radiation and Matter |
| 34 | Two measured spring constants in parallel — percentage error | Units and Measurements |
| 35 | Gas geyser heating flowing water — rate at which gas burns | Thermal Properties of Matter |
| 36 | Charge released on the axis of a vertical solenoid — its acceleration | Moving Charges and Magnetism |
| 37 | Work done moving a charge between two points | Electrostatic Potential and Capacitance |
| 38 | Logic circuit — which single gate it behaves as | Semiconductor Electronics |
| 39 | Rod hanging from two strings — tension the instant one is cut | Rotational Motion |
| 40 | Aluminium and steel rods joined — length after heating | Thermal Properties of Matter |
| 41 | Pulses sent along two joined strings — ratio of their travel times | Waves |
| 42 | Potential energy against distance — ranking the forces | Work, Energy and Power |
| 43 | Rod sliding in a magnetic field — force needed to keep it moving | Electromagnetic Induction |
| 44 | Horizontal tube with two standpipes — rate of flow | Mechanical Properties of Fluids |
| 45 | Loop in a field that varies as a sine — average heat in one period | Electromagnetic Induction |
| 46 numeric | Two rods joined — moment of inertia about a corner point | Rotational Motion |
| 47 numeric | Heat generated in a circuit in one minute | Current Electricity |
| 48 numeric | Beam expander — focal length of the second lens | Ray Optics |
| 49 numeric | Oxygen heated at constant volume — change in internal energy | Kinetic Theory of Gases |
| 50 numeric | Compound microscope — the magnification | Ray Optics |
Chapter by chapter
| Chapter | Questions | Marks |
|---|---|---|
| Electromagnetic Induction | 2 | 8 |
| Electrostatic Potential and Capacitance | 2 | 8 |
| Ray Optics | 2 | 8 |
| Rotational Motion | 2 | 8 |
| Thermal Properties of Matter | 2 | 8 |
| Units and Measurements | 2 | 8 |
| Atoms | 1 | 4 |
| Current Electricity | 1 | 4 |
| Dual Nature of Radiation and Matter | 1 | 4 |
| Electromagnetic Waves | 1 | 4 |
| Gravitation | 1 | 4 |
| Kinetic Theory of Gases | 1 | 4 |
| Laws of Motion | 1 | 4 |
| Mechanical Properties of Fluids | 1 | 4 |
| Moving Charges and Magnetism | 1 | 4 |
| Semiconductor Electronics | 1 | 4 |
| Wave Optics | 1 | 4 |
| Waves | 1 | 4 |
| Work, Energy and Power | 1 | 4 |
All 19 shifts of JEE Main 2026, counted together chapter by chapter: JEE Main Physics important chapters.
Twenty chapters for twenty-five questions.
Where the 100 marks sat
| Part of Physics | Questions | Marks | Share |
|---|---|---|---|
| Electrodynamics | 7 | 28 | 28% |
| Mechanics | 5 | 20 | 20% |
| Properties of Matter and Heat | 4 | 16 | 16% |
| Optics and Waves | 4 | 16 | 16% |
| Modern Physics and Electronics | 3 | 12 | 12% |
| Units, Dimensions and Measurement | 2 | 8 | 8% |
Electrodynamics opened the year where it stayed all through 2026, at 28 marks. Mechanics was a little lighter here than it would be in April, and optics and waves a little heavier.
How tough it was
| Level | Questions | Share | Which ones |
|---|---|---|---|
| Straight recall or one step | 6 | 24% | 28, 34, 36, 38, 40, 49 |
| Two or three steps | 14 | 56% | 26, 27, 29, 30, 31, 32, 33, 35, 37, 41, 42, 44, 48, 50 |
| Long or awkward | 5 | 20% | 39, 43, 45, 46, 47 |
Fewer gift questions than any April shift — only six could be finished on sight. The rod hanging from two strings and the two-rod moment of inertia were the two that ate the most clock. Nothing here was unfair, but very little was free either.
All 25 Physics questions, solved
Q1 · Gravitation · on the pattern of Q26
A satellite of mass 200 kg is in a circular orbit of radius 2RE. The energy that must be supplied to move it into a circular orbit of radius 4RE is α × 106 J. The value of α is ______. (RE = 6 × 106 m, g = 10 m/s2)
Answer 1500
Where it goes wrong Using only the potential energy. The satellite also slows down as it climbs, so the kinetic part must be counted, and that is exactly what the −GMm/2r form already does.
Q2 · Atoms · on the pattern of Q27
An alpha particle of energy 5.0 MeV is fired at a thin gold foil. The closest it can get to a gold nucleus is ______ m. (Atomic number of gold = 79, 1/4πε0 = 9 × 109 SI units, e = 1.6 × 10−19 C)
Answer about 4.55 × 10−14 m
Where it goes wrong Using e instead of 2e for the alpha particle. It is a helium nucleus and carries twice the electron’s charge.
Q3 · Electromagnetic Waves · on the pattern of Q28
The electric field in a plane electromagnetic wave is Ey = 60 sin[0.5 × 103 x − 1.5 × 1011 t] V/m. The magnetic field that goes with it is ______ T.
Answer Bz = 2 × 10−7 sin[0.5 × 103 x − 1.5 × 1011 t] T
Where it goes wrong Flipping a sign inside the bracket. The electric and magnetic fields of a plane wave rise and fall together; only the direction and the size differ.
Q4 · Units and Dimensions · on the pattern of Q29
Consider a changed Bernoulli equation: [P + A/(Bt)2] + ρg(h + Bt) + ½ρv2 = constant, where t has the dimensions of time. The dimensions of A and B respectively are ______.
Answer [MLT−2] and [M0LT−1]
Where it goes wrong Forgetting to square Bt. The extra L2 is what turns A from a pressure-like quantity into a force.
Q5 · Laws of Motion · on the pattern of Q30
A 2 kg mass starts from rest at the origin at t = 0 and moves under the force F = (6t2i − 4tj) N, with t in seconds. Its velocity and position at t = 2 s are ______.
Answer v = 8i − 4j m/s and r = 4i − 2.67j m
Where it goes wrong Using v = at and s = ½at2 with the value of a at t = 2. Those formulas need a constant acceleration, and here it keeps changing.
Q6 · Electrostatic Potential and Capacitance · on the pattern of Q31
A parallel plate capacitor has capacitance C with vacuum between the plates. A slab of thickness one quarter of the plate separation, with relative permittivity K, is slid in. The new capacitance is ______.
Answer 4KC/(3K + 1)
Where it goes wrong Multiplying the whole capacitance by K. That is only right when the slab fills the entire gap.
Q7 · Wave Optics · on the pattern of Q32
In a double slit experiment the slits are 0.2 cm apart and the screen is 80 cm away. One slit is covered with a transparent sheet of thickness t and refractive index 1.5, and the central fringe moves by 0.3 cm. The value of t is ______ cm.
Answer 1.5 × 10−3 cm
Where it goes wrong Writing nt instead of (n − 1)t. The sheet replaces an equal thickness of air, so only the difference counts.
Q8 · Dual Nature of Radiation · on the pattern of Q33
Light described by E = 50[sin(2 × 1015 t) + sin(8 × 1015 t)] (SI units) falls on a metal of work function 2.0 eV. The greatest kinetic energy of the ejected photoelectrons is about ______ eV. (h = 6.6 × 10−34 J·s, e = 1.6 × 10−19 C)
Answer about 3.25 eV
Where it goes wrong Reading 8 × 1015 as the frequency. It is the angular frequency, so it has to be divided by 2π before h is used.
Q9 · Units and Measurement · on the pattern of Q34
Two spring constants are measured as k1 = (20 ± 0.3) N/m and k2 = (30 ± 0.2) N/m. The springs are then joined in parallel. The percentage error in the equivalent spring constant is ______ %.
Answer 1 %
Where it goes wrong Adding the percentage errors instead of the absolute ones. Percentages add for products and quotients; for a sum it is the absolute errors that add.
Q10 · Thermal Properties of Matter · on the pattern of Q35
A gas geyser heats water flowing at 6.0 litre per minute from 25 °C to 75 °C. The rate at which the gas burns is ______ g/s. (Heat of combustion of the gas = 2.5 × 104 J/g, specific heat capacity of water = 4200 J/kg·°C)
Answer 0.84 g/s
Where it goes wrong Leaving the flow in litres per minute. Everything else is per second, so the rate has to be converted first.
Q11 · Moving Charges and Magnetism · on the pattern of Q36
A current-carrying solenoid is held vertically. A particle of mass m with charge Q is released from rest on the axis of the solenoid. Taking g as the acceleration due to gravity, the acceleration a of the particle satisfies ______.
Answer a = g
Where it goes wrong Assuming a magnetic field must slow the charge down. A magnetic force needs the velocity to cross the field; parallel to it, there is no force at all.
Q12 · Electrostatic Potential · on the pattern of Q37
A point charge of 2 × 10−8 C sits at the origin. A charge of 3 μC is carried from the point A(6, 6, 3) m to the point B(2, 2, 1) m. The work that has to be done by an outside agent is ______ J. (1/4πε0 = 9 × 109 SI units)
Answer 1.2 × 10−4 J
Where it goes wrong Using the straight-line distance from A to B. Only the two distances from the source charge matter, because the field is conservative.
Q13 · Semiconductor Electronics · on the pattern of Q38
Two inputs A and B each pass through a NOT gate, and the two outputs feed an OR gate. The whole circuit works as a ______ gate.
Answer NAND gate
Where it goes wrong Answering NOR. NOR is (A + B)′; this circuit is the other De Morgan pair.
Q14 · Rotational Motion · on the pattern of Q39
A uniform rod of mass m and length l hangs horizontally from two identical light inextensible strings, one tied at each end. One string is cut. The tension in the other string immediately afterwards is ______.
Answer mg/4
Where it goes wrong Answering mg/2, which is the tension before the cut. The moment the rod is free to turn, the centre of mass starts accelerating and the tension drops.
Q15 · Thermal Properties of Matter · on the pattern of Q40
An aluminium rod and a steel rod of equal length and cross-section are joined end to end to make a total length of 100 cm at 20 °C. The coefficients of linear expansion are 24 × 10−6 /°C for aluminium and 12 × 10−6 /°C for steel. The length of the composite rod at 120 °C is ______ cm.
Answer 100.18 cm
Where it goes wrong Using 100 cm as the length of each piece. The two together make 100 cm, so each starts at 50.
Q16 · Waves · on the pattern of Q41
Two strings A and B, of linear densities 1 × 10−4 kg/m and 4 × 10−4 kg/m and lengths 3.0 m and 2.0 m, are joined end to end. The free ends are tied to rigid supports and the tension throughout is 400 N. Identical pulses are sent in from the two far ends at the same instant and take times t1 and t2 to reach the joint. The ratio t1/t2 is ______.
Answer 3 : 4
Where it goes wrong Assuming the heavier string carries the pulse faster. A larger linear density sits in the denominator, so it slows the pulse down.
Q17 · Work, Energy and Power · on the pattern of Q42
The potential energy of a particle changes along x as a straight line in four regions: over AB it rises 4 J in 2 m, over BC it stays flat for 3 m, over CD it falls 6 J in 1 m, and over DE it rises 3 J in 3 m. Ranking the magnitudes of the force on the particle from largest to smallest gives ______.
Answer FCD > FAB > FDE > FBC
Where it goes wrong Ranking by the height of the graph instead of its slope. A large potential energy with a flat graph means no force at all.
Q18 · Electromagnetic Induction · on the pattern of Q43
A 1 m long metal rod slides on rails and completes a circuit whose plane is perpendicular to a magnetic field of 0.20 T. The total resistance of the circuit is 4 Ω. The force needed to keep the rod moving to the right at a steady 2.0 m/s is ______ N.
Answer 0.02 N
Where it goes wrong Expecting zero force because the speed is constant. Constant speed means no net force, which is exactly why the push must equal the magnetic drag.
Q19 · Mechanical Properties of Fluids · on the pattern of Q44
Water flows through a horizontal tube. Two vertical standpipes show a height difference of 4 cm between points A and B, where the cross-sections are 8 cm2 and 4 cm2. The rate of flow is about ______ cm3/s. (g = 10 m/s2)
Answer about 413 cm3/s
Where it goes wrong Mixing metres and centimetres halfway through. Work the speed out in SI, then convert once at the end.
Q20 · Electromagnetic Induction · on the pattern of Q45
A conducting circular loop of area 2.0 m2 lies perpendicular to a magnetic field B = sin(50t) tesla. The resistance of the loop is 50 Ω. The average thermal energy dissipated in the loop over one full period is ______ J.
Answer 4π J, about 12.6 J
Where it goes wrong Using the peak emf for the power. The average of a squared sine is half, which is where the factor of 2 in 2R comes from.
Q21 · Rotational Motion · numeric · on the pattern of Q46
Two identical thin rods, each of mass M and length L, are joined into a T shape: the second rod is attached by its own centre to one end of the first and lies at right angles to it. The moment of inertia of the pair about an axis through the free end P of the first rod, perpendicular to the plane of the two rods, is (x/12)ML2. The value of x is ______.
Answer 17
Where it goes wrong Treating the second rod as a point mass at L, which gives 12/12 and misses the ML2/12 of its own spread.
Q22 · Current Electricity · numeric · on the pattern of Q47
A 9 V battery with an internal resistance of 1 Ω is connected across a 3 Ω and a 6 Ω resistor joined in parallel. The heat generated in those two resistors in one minute is ______ J.
Answer 1080 J
Where it goes wrong Dropping the internal resistance when working out the current. It is only left out of the heat, not out of the circuit.
Q23 · Ray Optics · numeric · on the pattern of Q48
A collimated beam of light 3 mm across travels along the x-axis. It is to be widened into a collimated beam 15 mm across using two convex lenses. If the first lens has a focal length of 30 mm, the focal length of the second lens is ______ mm.
Answer 150 mm
Where it goes wrong Trying to use the lens formula. Both the incoming and outgoing beams are parallel, so only the ratio of focal lengths matters.
Q24 · Kinetic Theory of Gases · numeric · on the pattern of Q49
8 mole of oxygen is heated at constant volume from 20 °C to 45 °C. The change in the internal energy of the gas is ______ calorie. (Molar specific heat at constant pressure CP = 7 cal/mol·°C, R = 2 cal/mol·°C)
Answer 1000 calorie
Where it goes wrong Using CP because the value is the one given. ΔU always uses CV, and CP is given only so that CV can be found.
Q25 · Ray Optics · numeric · on the pattern of Q50
In a compound microscope the objective has focal length 2 cm, the eyepiece has focal length 5 cm and the tube length is 25 cm. The magnification for normal adjustment is ______. (Least distance of distinct vision = 25 cm)
Answer 62.5
Where it goes wrong Using (1 + D/fe) for the eyepiece. That form is for the image held at the near point, not at infinity.
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 January 2026 shifts were held on 21, 22, 23, 24 and 28 January, two shifts a day.
All shifts, date by date: JEE Main Previous Years Papers.
Sit a paper in the same shape, free
25 questions. 45 minutes. Out of 100. Marked the way JEE Main marks it, with a hint and the answer key for every question you miss. No payment, no card, and no account needed to start.
Reading a past paper tells you what was asked. Sitting one on the clock tells you what you can do. Only the second one moves your score.