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JEE Main (Jan 7) - Morning Shift | 2020
Q. Consider a circular coil of wire carrying constant current I, forming a magnetic dipole. The magnetic flux through an infinite plane contains the circular coil and excluding the circular coil area is given by Φi. The magnetic flux through the area of the circular coil area is given by Φ0
Which of the following options is correct?
  1. Φi<Φ0
  2. Φi=Φ0
  3. Φi>Φ0
  4. Φi=Φ0
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Q. The radius of gyration of a uniform rod of length l, about an axis passing through a point l4 away from the centre of the rod, and perpendicular to it, is :
  1. 748l
  2. 38l
  3. 18l
  4. 14l
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Q. Speed of a transverse wave on a straight wire (mass 6.0 g, length 60 cm) and area of cross-section (1.0 mm2) is 90ms1. If the Young's modulus of wire is 16×1011Nm2, the extension of wire over its natural length is :
  1. 0.01mm
  2. 0.03mm
  3. 0.02mm
  4. 0.04mm
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Q. A litre of dry air at STP expands adiabatically to a volume of 3 litres. If γ=1.40, the work done by air is: (31.4=4.6555) [Take air to be an ideal gas]
  1. 48J
  2. 100.8J
  3. 60.7J
  4. 90.5J
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Q.
Two infinite planes each with uniform surface charge density +σ are kept in such a way that the angle between them is 300. The electric field in the region shown between them is given by :
1697151_9b005ede907440cd9e7b130caa9c6576.png
  1. σ2ϵ0[(132)^y^x2]
  2. σ2ϵ0[(1+32)^y+^x2]
  3. σ2ϵ0[(1+3)^y+^x2]
  4. σ2ϵ0[(1+3)^y^x2]
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Q. Two moles of an ideal gas with CPCV=53 are mixed with 3 moles of another ideal gas with CPCV=43. The value of CPCV for the mixture is :
  1. 1.47
  2. 1.45
  3. 1.42
  4. 1.50
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Q. As shown in the figure, a bob of mass m is tied by a massless string whose other end portion is wound on a fly wheel (disc) of radius r and mass m. When released from rest the bob starts falling vertically. When it has covered a distance of h, the angular speed of the wheel will be :
1697155_e72cd2d1a8e04ca88fd960312c152f32.png
  1. r34gh
  2. 1r4gh3
  3. r32gh
  4. 1r2gh3
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Q. A satellite of mass m is launched vertically upwards with an initial speed u from the surface of the earth. After it reaches height R(R= radius of the earth), it ejects a rocket of mass m10 so that subsequently the satellite moves in a circular orbit. The kinetic energy of the rocket is (G is the gravitational constant; M is the mass of the earth) :
  1. m20(u2+113200GMR)
  2. 5m(u2119200GMR)
  3. m20(u2GM3R)2
  4. 3m8(u+5GM6R)2
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Q. A long solenoid of radius R carries a time (t)-dependent current I(t)=I0t(1t). A ring of radius 2R is placed coaxially near its middle. During the time interval 0t1, the induced current (IR) and the induced EMF(VR) in the ring change as:
  1. At t=0.5 direction of IR reverses and VR is zero.
  2. Direction if IR remains unchanged and VR is zero at t=0.25
  3. At t=0.25 direction of IR reverses and VR is maximum.
  4. Direction of IR remains unchanged and VR is maximum at t=0.5
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Q. The time period of revolution of electron in its ground state orbit in a hydrogen atom is 1.6×1016 s. The frequency of revolution of the electron in its first excited state (in s1) is:
  1. 5.6×1012
  2. 1.6×1014
  3. 6.2×1015
  4. 7.8×1014
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Q. If the magnetic field in a plane electromagnetic wave is given by
B=3×108sin(1.6×103x+48×1010t)^j T, then what will be expression for electric field?
  1. E=3×108sin(1.6×103x+48×1010t)^j V/m
  2. E=60sin(1.6×103x+48×1010t)^k V/m
  3. E=9sin(1.6×103x+48×1010t)^k V/m
  4. E=3×108sin(1.6×103x+48×1010t)^i V/m
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Q. If we need a magnification of 375 from a compound microscope of tube length 150mm and an objective of focal length 5mm, the focal length of the eye-piece, should be close to :
  1. 2 mm
  2. 12 mm
  3. 33 mm
  4. 22 mm
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Q. Three point particles of masses 1.0kg, 1.5kg and 2.5kg are placed at three corners of a right angle triangle of sides 4.0cm, 3.0cm and 5.0cm as shown in the figure. The centre of mass of the system is at a point :
1697175_adb3c67a83864716bf13599725ce8a2e.png
  1. 1.5 cm right and 1.2 cm above 1 kg mass
  2. 2.0 cm right and 0.9 cm above 1 kg mass
  3. 0.6 cm right and 2.0 cm above 1 kg mass
  4. 0.9 cm right and 2.0 cm above 1 kg mass
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Q. Visible light of wavelength 6000×108cm falls normally on a single slit and produces a diffraction pattern. It is found that the second diffraction minimum is at 600 from the central maximum. if the first minimum is produced at θ1 then θ1 is close to :
  1. 250
  2. 300
  3. 200
  4. 450
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Q. Which of the following gives a reversible operation ?
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Q. A 60HP electric motor lifts an elevator having a maximum total load capacity of 2000kg. If the frictional force on the elevator is 4000N, the speed of the elevator at full load is close to : (1 HP=746W, g=10ms2)
  1. 1.5ms1
  2. 1.9ms1
  3. 1.7ms1
  4. 2.0ms1
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Q.

A parallel plate capacitor has plates of area 'A' separated by distance 'd' between them. It is filled with a dielectric which has a dielectric constant that varies as k(x)=K(1+αx) where 'x' is the distance measured from one of the plates. If (αd)<<1, the total capacitance of the system is best by the expression:
1697191_19d13820ad4b4a96aa13f9bdb6a5b13f.png
  1. Aϵ0Kd(1+(αd2)2)
  2. Aϵ0Kd(1+α2d22)
  3. Aϵ0Kd(1+αd2)
  4. Aϵ0d(1+αd)
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Q. A LCR circuit behaves like a damped harmonic oscillator. Comparing it with a physical spring-mass damped oscillator having damping constant 'b', the correct equivalence would be :
  1. Lm, Ck, Rb
  2. L1b, C1m, R1k
  3. Lk, Cb, Rm
  4. Lm, C1k, Rb
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Q. The current I1 (in A) flowing through 1Ω resistor in the above circuit is :
1697200_922b766870e240489c8e0c054367a367.png
  1. 0.25
  2. 0.2
  3. 0.5
  4. 0.4
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Q. A polarizer -analyser set is adjusted such that the intensity of light coming out of the analyser is just 10% of the original intensity. Assuming that the polarizer-analyser set does not absorb any light, the angle by which the analyser need to be rotated further to reduce the output intensity to be zero, is:
  1. 900
  2. 71.60
  3. 18.40
  4. 450
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Q. A loop ABCDEFA of straight edges has six corner points A(0, 0, 0), B(5, 0, 0), C(5, 5, 0), D(0, 5, 0), E(0, 5, 5) abd F(0, 0, 5). The magnetic field in this region is B=(3^i+4^k)T. The quantity of flux through the loop ABCDEFA (in Wb) is ______.
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Q. In the following reactions, products (A) and (B), respectively, are:
NaOH+(hot and conc.)Cl2(A)+ side products
Ca(OH)2(dry)+Cl2(B)+ side products

  1. NaOCl and Ca(ClO3)2
  2. NaClO3 and Ca(ClO3)2
  3. NaClO3 and Ca(OCl)2
  4. NaOCl and Ca(OCl)2
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Q. A non-isotropic solid metal cube has coefficients of linear expansion as: 5×105/oC along the x-axis and 5×106/oC along the y and the z-axis. If the coefficient of volume expansion of the solid is C×106/oC then the value of C is ______.
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Q. A carnot engine operates between two reservoirs of temperature 900K and 300K. The engine performs 1200J of work per cycle. The heat energy (in J) delivered by the engine to the low temperature reservoir, in a cycle, is_________ .
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Q. Consider the following reactions:
Which of these reactions are possible ?
1697211_298c93b1cf1541c68318c4fc544a44cf.png
  1. (b) and (d)
  2. (b), (c) and (d)
  3. (a) and (d)
  4. (a) and (b)
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Q. Two open beakers one containing a solvent and the other containing a mixture of that solvent with a non volatile solute are together sealed in a container. Over time:
  1. The volume of the solution does not change and the volume of the solvent decreases
  2. the volume of the solution deceases and the volume of the solvent increases
  3. the volume of the solution and the solvent does not change
  4. the volume of the solution increases and the volume of the solvent decreases
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Q. A beam of electromagnetic radiation of intensity 6.4×105W/cm2 is comprised of wavelength, λ=310nm. It falls normally on a metal (work function φ=2eV) of surface area of 1cm2. If one in 103 photons ejects an electron, total number of electrons ejected in 1 s is 10x.
(hc=1240eVnm, 1eV=1.6×1019J), then x is ______.
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Q. Which of the following statements is correct ?
  1. Gluconic acid is a partial oxidation product of glucose
  2. Gluconic acid is a dicarboxylic acid
  3. Gluconic acid is obtained by oxidation of glucose with HNO3
  4. Gluconic acid can form cyclic (acetal/ hemiacetal) structure
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Q. A particle (m=1kg) slides down a frictionless rack (AOC) starting from rest at a point A (height 2m). After reaching C, the particle continuous to move freely in air as a projectile. When it reaching its highest point P (height 1m), the kinetic energy of the particle (in J) is : (Figure drawn is schematic and not to scale; take g=10ms2)______.
1697219_1743febff97a40fcb26b623f6e939a5e.png
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Q. Among the statements (a)-(d), the incorrect ones are:
(a) Octahedral Co(III) complexes with strong field ligands have very high magnetic moments
(b) When Δ0<P, the d-electron configuration of Co(III) in an octahedral complex is t4ege2g
(c) Wavelength of light absorbed by [Co(en)3]3+ is lower than that of [CoF6]3
(d) If the Δ0 for an octahedral complex of Co(III) is 18, 000 cm1, the Δt for its tetrahedral complex with the same ligand will be 16, 000 cm1
  1. (b) and (c) only
  2. (a) and (d) only
  3. (a) and (b) only
  4. (c) and (d) only
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