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JEE Main 2021 February 24, Shift 1 Question Paper with Solutions

All 90 questions from the JEE Main 2021 (February 24, Shift 1) shift — Physics (30), Chemistry (30) and Mathematics (30) — each with the correct answer (answer key) and a step-by-step solution. Read it free online, or attempt the full paper as a timed mock test.

Physics30 questions

Q1Single correctUnits and Measurements
The work done by a gas molecule in an isolated system is given by, , where x is the displacement, k is the Boltzmann constant and T is the temperature. and are constants. Then the dimensions of will be:
(A)
(B)
(C)
(D)
Q2Single correctKinematics
If the velocity-time graph has the shape AMB, what would be the shape of the corresponding acceleration-time graph?
Velocity-time graph shaped AMB: from A (top-left, positive V) a straight line descends to M (vertex below the t-axis) then rises to B (top-right), with a dashed horizontal line joining A and B.
(A)
(B)
(C)
(D)
Q3Single correctRotational Motion
Moment of inertia (M.I.) of four bodies, having same mass and radius, are reported as;
M.I. of thin circular ring about its diameter,
M.I. of circular disc about an axis perpendicular to disc and going through the centre,
M.I. of solid cylinder about its axis and
M.I. of solid sphere about its diameter.
Then:
(A)
(B)
(C)
(D)
Q4Single correctGravitation
Consider two satellites and with periods of revolution 1hr and 8hr respectively revolving around a planet in circular orbits. The ratio of angular velocity of satellite to the angular velocity of satellite is:
(A)
(B)
(C)
(D)
Q5Single correctGravitation
Four identical particles of equal masses 1 kg made to move along the circumference of a circle of radius 1 m under the action of their own mutual gravitational attraction. The speed of each particle will be:
(A)
(B)
(C)
(D)
Q6Single correctGravitation
Two stars of masses and at a distance rotate about their common centre of mass in free space. The period of revolution is:
(A)
(B)
(C)
(D)
Q7Single correctProperties of Solids and Liquids
If Y, K and are the values of Young's modulus, bulk modulus and modulus of rigidity of any material respectively. The correct relation for these parameters is:
(A)
(B)
(C)
(D)
Q8Single correctProperties of Solids and Liquids
Each side of a box made of metal sheet in cubic shape is a at room temperature T, the coefficient of linear expansion of the metal sheet is . The metal sheet is heated uniformly, by a small temperature , so that its new temperature is . Calculate the increase in the volume of the metal box.
(A)
(B)
(C)
(D)
Q9Single correctThermodynamics
Match List I with List II.
List IList II
(a). Isothermal(i). Pressure constant
(b). Isochoric(ii). Temperature constant
(c). Adiabatic(iii). Volume constant
(d). Isobaric(iv). Heat content is constant
(A)
(B)
(C)
(D)
Q10Single correctThermodynamics
n mole of a perfect gas undergoes a cyclic process ABCA (see figure) consisting of the following processes.
: Isothermal expansion at temperature T so that the volume is doubled from to and pressure changes from to .
: Isobaric compression at pressure to initial volume .
: Isochoric change leading to change of pressure from to .
Total work done in the complete cycle ABCA is:
P-V diagram of cycle ABCA: A at (V1,P1), curved path A to B down to (V2=2V1,P2), isobaric B to C leftwards at P2 to V1, isochoric C to A upwards at V1.
(A)
(B)
(C)
(D)
Q11Single correctOscillations and Waves
In the given figure, a mass is attached to a horizontal spring which is fixed on one side to a rigid support. The spring constant of the spring is . The mass oscillates on a frictionless surface with time period and amplitude . When the mass is in equilibrium position, as shown in the figure, another mass is gently fixed upon it. The new amplitude of oscillation will be:
Block M on a hatched horizontal floor attached by a horizontal spring of constant k to a hatched wall on the right.
(A)
(B)
(C)
(D)
Q12Single correctElectrostatics
A cube of side has point charges located at each of its vertices except at the origin where the charge is . The electric field at the centre of cube is:
Cube of side a with axes x (up), y (front-left), z (right); +Q at seven vertices and -Q at the origin vertex.
(A)
(B)
(C)
(D)
Q13Single correctElectrostatics
Two equal capacitors are first connected in series and then in parallel. The ratio of the equivalent capacities in the two cases will be:
(A)
(B)
(C)
(D)
Q14Single correctCurrent Electricity
A current through a wire depends on time as , where A and A . Find the charge crossed through a section of the wire in 15 s.
(A)
(B)
(C)
(D)
Q15Single correctCurrent Electricity
A cell of emf 6 V and internal resistance is connected with another cell of emf 4 V and internal resistance 8 (as shown in the figure). The potential difference across points X and Y is:
Series loop: from P, cell E1 (6 V, 2 ohm), node X, cell E2 (4 V, 8 ohm), to Y, with a rectangular return wire from P to Y.
(A)
(B)
(C)
(D)
Q16Single correctOptics
The focal length is related to the radius of curvature of the spherical convex mirror by:
(A)
(B)
(C)
(D)
Q17Single correctOptics
In a Young's double slit experiment, the width of the one of the slit is three times the other slit. The amplitude of the light coming from a slit is proportional to the slit-width. Find the ratio of the maximum to the minimum intensity in the interference pattern.
(A)
(B)
(C)
(D)
Q18Single correctDual Nature of Matter and Radiation
Given below are two statements:
Statement I: Two photons having equal linear momenta have equal wavelengths.
Statement II: If the wavelength of the photon is decreased, then the momentum and energy of a photon will also decrease.
In the light of the above statements, choose the correct answer from the options given below.
(A)
(B)
(C)
(D)
Q19Single correctAtoms and Nuclei
In the given figure, the energy levels of hydrogen atom have been shown along with some transitions marked and .
The transitions and respectively represent
Hydrogen energy-level diagram (n=1 at -13.6 eV up to 0 eV with a Continuum box), with downward transition arrows A (n2->n1), B (n5->n2), C (0 eV->n3), D (n4->n2), E (0 eV->n1).
(A)
(B)
(C)
(D)
Q20Single correctElectronic Devices
If an emitter current is changed by mA, the collector current changes by mA. The value of will be:
(A)
(B)
(C)
(D)
Q21NumericalLaws of Motion
The coefficient of static friction between a wooden block of mass kg and a vertical rough wall is . The magnitude of the horizontal force that should be applied on the block to keep it adhere to the wall will be________N. m
Q22NumericalLaws of Motion
An inclined plane is bent in such a way that the vertical cross-section is given by where y is in vertical and x in horizontal direction. If the upper surface of this curved plane is rough with coefficient of friction , the maximum height in cm at which a stationary block will not slip downward is________cm.
Q23NumericalWork, Energy and Power
A ball with a speed of m collides with another identical ball at rest. After the collision, the direction of each ball makes an angle of with the original direction. If the ratio of velocities of the balls after the collision is x:y, then what is the value of x?
Q24NumericalProperties of Solids and Liquids
A hydraulic press can lift kg when a mass m is placed on the smaller piston. It can lift ____ kg when the diameter of the larger piston is increased by times and that of the smaller piston is decreased by times keeping the same mass m on the smaller piston.
Q25NumericalElectromagnetic Induction and Alternating Currents
A common transistor radio set requires V D.C. for its operation. The D.C. source is constructed by using a transformer and a rectifier circuit, which are operated at V A.C. on standard domestic A.C. supply. The number of turns of secondary coil are , then the number of turns of primary are________.
Q26NumericalElectromagnetic Induction and Alternating Currents
A resonance circuit having inductance and resistance H and respectively oscillates at MHz frequency. The value of quality factor of this resonator is________.
Q27NumericalElectromagnetic Waves
An electromagnetic wave of frequency 5GHz, is travelling in a medium whose relative electric permittivity and relative magnetic permeability both are . Its velocity in this medium is ____ m .
Q28NumericalOptics
An unpolarized light beam is incident on the polarizer of a polarization experiment and the intensity of light beam emerging from the analyzer is measured as 100 Lumens. Now, if the analyzer is rotated around the horizontal axis (direction of light) by in clockwise direction, the intensity of emerging light will be________Lumens.
Q29NumericalCurrent Electricity
In connection with the circuit drawn below, the value of current flowing through k resistor is________ A.
Zener regulator: 10 V battery, a 2 k-ohm resistor and a 5 V Zener diode in parallel, with a 1 k-ohm series resistor in the top rail.
Q30NumericalElectromagnetic Waves
An audio signal amplitude modulates a carrier . The value of percent modulation is

Chemistry30 questions

Q31Single correctClassification of Elements and Periodicity in Properties
Consider the elements Mg, Al, S, P and Si, the correct increasing order of their first ionisation enthalpy is:
(A)
(B)
(C)
(D)
Q32Single correctChemical Bonding and Molecular Structure
Which of the following are isostructural pairs?
A. and
B. and
C. and
D. and
(A)
(B)
(C)
(D)
Q33Single correctRedox Reactions and Electrochemistry
(A)
(B)
Choose the correct option.
(A)
(B)
(C)
(D)
Q34Single correctp-Block Elements
was leached with alkali to get X. The solution of X on passing of gas Y, forms Z. X, Y and Z respectively are
(A)
(B)
(C)
(D)
Q35Single correctOrganic Compounds Containing Oxygen
Identify products A and B.
1-methylcyclopentene reacting: dil. KMnO4 / 275 K gives A, then CrO3 gives B.
(A)
(B)
(C)
(D)
Q36Single correctOrganic Compounds Containing Oxygen
Which of the following compound gives pink colour on reaction with phthalic anhydride in conc. followed by treatment with NaOH?
(A)
(B)
(C)
(D)
Q37Single correctHydrocarbons
In the following reaction, the reason why meta-nitro product also formed is:
Aniline + Conc. HNO3 / Conc. H2SO4, 288 K gives [A] para-nitroaniline 51% + [B] meta-nitroaniline 47% + [C] ortho-nitroaniline 2%.
(A)
(B)
(C)
(D)
Q38Single correctp-Block Elements
The gas released during anaerobic degradation of vegetation may lead to:
(A)
(B)
(C)
(D)
Q39Single correctSome Basic Concepts in Chemistry
In Freundlich adsorption isotherm, slope of AB line is:
Freundlich isotherm: log(x/m) on the vertical axis versus log P, a straight line AB rising left-to-right through points A (lower) and B (upper).
(A)
(B)
(C)
(D)
Q40Single correctd- and f-Block Elements
Which of the following ore is concentrated using group 1 cyanide salt?
(A)
(B)
(C)
(D)
Q41Single correctd- and f-Block Elements
The major components in "Gun Metal" are:
(A)
(B)
(C)
(D)
Q42Single correctd- and f-Block Elements
The electrode potential of of 3 d-series elements shows positive value for?
(A)
(B)
(C)
(D)
Q43Single correctOrganic Compounds Containing Halogens
The product formed in the first step of the reaction of the following compound with excess Mg / (Et ) is:
3,5-dibromohexane: CH3-CH2-CH(Br)-CH2-CH(Br)-CH3 with Br on the third and fifth carbons.
(A)
(B)
(C)
(D)
Q44Single correctHydrocarbons
What is the major product formed by HI on reaction with the following compound?
3,3-dimethylbut-1-ene: (CH3)3C-CH=CH2.
(A)
(B)
(C)
(D)
Q45Single correctOrganic Compounds Containing Oxygen
What is the final product (major) 'A' in the given reaction?
Major product among the following is?
1-(2-methylcyclohexyl)ethan-1-ol: cyclohexane ring with a CH3 on one carbon and a CH(OH)CH3 group on the adjacent carbon, reacting with HCl.
(A)
(B)
(C)
(D)
Q46Single correctOrganic Compounds Containing Oxygen
Which of the following reagent is used for the following reaction?
(A)
(B)
(C)
(D)
Q47Single correctOrganic Compounds Containing Nitrogen
A and B in the following reactions are:
Aniline reacts with NaNO2/HCl then KCN to give (A); (A) reacts with SnCl2/HCl/H3O+ to give (B).
(A)
(B)
(C)
(D)
Q48Single correctSome Basic Principles of Organic Chemistry
Match List I with List II.
List I (Monomer Unit)List II (Polymer)
(a). Caprolactum(i). Natural rubber
(b). - Chloro- - butadiene(ii). Buna-N
(c). Isoprene(iii). Nylon 6
(d). Acrylonitrile(iv). Neoprene
(A)
(B)
(C)
(D)
Q49Single correctd- and f-Block Elements
Given below are two statements:
Statement I: Colourless cupric metaborate is reduced to cuprous metaborate in a luminous flame.
Statement II: Cuprous metaborate is obtained by heating boric anhydride and copper sulphate in a non-luminous flame.
In the light of the above statements, choose the most appropriate answer from the options given below.
(A)
(B)
(C)
(D)
Q50Single correctBiomolecules
Out of the following, which type of interaction is responsible for the stabilisation of - helix structure of proteins?
(A)
(B)
(C)
(D)
Q51NumericalSome Basic Concepts in Chemistry
g of compound AM .W . was used to make mL of its aqueous solution. The molarity of the solution in M is . The value of x is_____ (Rounded off to the nearest integer)
Q52NumericalAtomic Structure
A proton and a nucleus are accelerated by the same potential. If and denote the de Broglie wavelengths of and proton respectively, then the value of is . The value of x is _____ (Rounded off to the nearest integer) [Mass of mass of proton]
Q53NumericalEquilibrium
For the reaction , the value of the equilibrium constant at K and atm is equal to . The value of for the reaction at K and atm in is , where x is (Rounded off to the nearest integer) and
Q54NumericalCoordination Compounds
The stepwise formation of is given below:




The value of stability constants and are and respectively. The overall equilibrium constants for dissociation of is . The value of x is _____ (Rounded off to the nearest integer)
Q55NumericalEquilibrium
At K and atm pressure, there are equal number of molecules and Cl atoms in the reaction mixture. The value of for the reaction under the above conditions is . The value of x is _____ (Rounded off to the nearest integer)
Q56NumericalRedox Reactions and Electrochemistry
The reaction of sulphur in alkaline medium is given below:

The values of 'a' is _____ (Integer answer)
Q57Numericalp-Block Elements
Number of amphoteric compounds among the following is
(A) BeO
(B) BaO
(C) BeO
(D) Sr O
Q58NumericalSome Basic Concepts in Chemistry
The coordination number of an atom in a body-centered cubic structure is_____ [Assume that the lattice is made up of atoms.]
Q59NumericalSolutions
When g of is added to mL of water, its freezing point drops by C. The dissociation constant of is . The value of x is off to the nearest integer)
Q60NumericalChemical Kinetics
Gaseous cyclobutene isomerizes to butadiene in a first order process which has a 'K' value of at C. The time in minutes it takes for the isomerization to proceed to completion at this temperature is_____. (Rounded off to the nearest integer)

Mathematics30 questions

Q61Single correctComplex Numbers and Quadratic Equations
Let p and q be two positive numbers such that and . Then p and q are roots of the equation:
(A)
(B)
(C)
(D)
Q62Single correctPermutations and Combinations
A scientific committee is to be formed from 6 Indians and 8 foreigners, which includes at least 2 Indians and double the number of foreigners as Indians. Then the number of ways, the committee can be formed, is:
(A)
(B)
(C)
(D)
Q63Single correctSequence and Series
If satisfies the equation , then the value of , where , is equal to
(A)
(B)
(C)
(D)
Q64Single correctCo-ordinate Geometry
A man is walking on a straight line. The arithmetic mean of the reciprocals of the intercepts of this line on the coordinate axes is . Three stones A,B and C are placed at the points and respectively. Then which of these stones is / are on the path of the man?
(A)
(B)
(C)
(D)
Q65Single correctBinomial Theorem and its Simple Applications
The value of is equal to
(A)
(B)
(C)
(D)
Q66Single correctCo-ordinate Geometry
The locus of the mid-point of the line segment joining the focus of the parabola to a moving point of the parabola, is another parabola whose directrix is:
(A)
(B)
(C)
(D)
Q67Single correctSets, Relations and Functions
The statement among the following that is a tautology is:
(A)
(B)
(C)
(D)
Q68Single correctTrigonometry
Two vertical poles are m apart and the height of one is three times that of the other. If from the middle point of the line joining their feet, an observer finds the angles of elevation of their tops to be complementary, then the height of the shorter pole (in meters) is:
(A)
(B)
(C)
(D)
Q69Single correctMatrices and Determinants
The system of linear equations



is inconsistent if :
(A)
(B)
(C)
(D)
Q70Single correctSets, Relations and Functions
Let be defined as and be defined as . Then the composition function f(g(x)) is:
(A)
(B)
(C)
(D)
Q71Single correctLimit, Continuity and Differentiability
If is a function defined by , where denotes the greatest integer function, then f is:
(A)
(B)
(C)
(D)
Q72Single correctLimit, Continuity and Differentiability
The function :
(A)
(B)
(C)
(D)
Q73Single correctCo-ordinate Geometry
If the tangent to the curve at the point meets the curve again at Q, then the ordinate of the point which divides PQ internally in the ratio is:
(A)
(B)
(C)
(D)
Q74Single correctIntegral Calculus
If , where c is a constant of integration, then the ordered pair a,b is equal to:
(A)
(B)
(C)
(D)
Q75Single correctIntegral Calculus
is equal to:
(A)
(B)
(C)
(D)
Q76Single correctIntegral Calculus
The area (in sq. units) of the part of the circle , which is outside the parabola , is equal to
(A)
(B)
(C)
(D)
Q77Single correctDifferential Equations
The population at time t of a certain species follows the differential equation . If , then the time at which population becomes zero is:
(A)
(B)
(C)
(D)
Q78Single correctThree Dimensional Geometry
The distance of the point from the point of intersection of the line and the plane is:
(A)
(B)
(C)
(D)
Q79Single correctThree Dimensional Geometry
The equation of the plane passing through the point and perpendicular to the planes and , is
(A)
(B)
(C)
(D)
Q80Single correctStatistics and Probability
An ordinary dice is rolled for a certain number of times. If the probability of getting an odd number 2 times is equal to the probability of getting an even number 3 times, then the probability of getting an odd number for odd number of times is:
(A)
(B)
(C)
(D)
Q81NumericalComplex Numbers and Quadratic Equations
If the least and the largest real values of , for which the equation and has a solution, are p and q respectively; then is equal to______.
Q82NumericalCo-ordinate Geometry
If one of the diameters of the circle is a chord of another circle C, whose center is at , then its radius is______.
Q83NumericalSequence and Series
Let and for some . If the sum of all the elements of the set is , then l is equal to______.
Q84NumericalMatrices and Determinants
Let , where . Suppose is a matrix satisfying for some non-zero . If and , then is equal to______.
Q85NumericalMatrices and Determinants
Let M be any matrix with entries from the set . The maximum number of such matrices, for which the sum of diagonal elements of is seven, is______.
Q86NumericalTrigonometry
is equal to______.
Q87NumericalTrigonometry
The minimum value of for which the equation has at least one solution in is______.
Q88NumericalIntegral Calculus
If , and x denotes the greatest integer , then is equal to______.
Q89NumericalVector Algebra
Let three vectors and be such that is coplanar with and , and is perpendicular to , where and , then the value of is ______.
Q90NumericalStatistics and Probability
Let be three independent events in a sample space. The probability that only occur is , only occurs is and only occurs is . Let p be the probability that none of the events occurs and these 4 probabilities satisfy the equations and (All the probabilities are assumed to lie in the interval ) Then is equal to______.

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Frequently Asked Questions

How many questions are in the JEE Main 2021 February 24, Shift 1 paper?

The JEE Main 2021 February 24, Shift 1 paper has 90 questions — Physics (30), Chemistry (30) and Mathematics (30). Every question is on this page with its correct answer and a step-by-step solution.

What is the marking scheme for JEE Main?

JEE Main awards +4 marks for each correct answer and −1 for a wrong answer, with 0 for questions left unattempted. The paper covers Physics, Chemistry and Mathematics.

Are the answer key and step-by-step solutions provided for the 2021 February 24, Shift 1 paper?

Yes — every question shows the correct answer (answer key) and a detailed step-by-step solution, free to read online.

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