Magnetism & Matter PYQs Set 3 (PDF)

Set 3 of 6 · Questions 61-90 of 176

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Mere Teacher · Previous Year Questions JEE Main Physics · Magnetism & Matter · Set 3 (Q61-90)
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61. $Given below are two statements: Statement I: The diamagnetic property depends on temperature Statement II: The induced magnetic dipole moment in a diamagnetic sample is always opposite to the magnetising field In the light of given statements, choose the correct answer from the options given below$ (1) $Both Statement I and Statement II are False$ (2) $Statement I is incorrect but Statement II is true$ (3) $Statement I is correct but Statement II is false$ (4) $Both Statement I and Statement II are true$ 62. $A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60^{\circ} is W. Now the torque required to keep the magnet in this new position is [NEET 2016]$ (1) $\frac{W}{3}$ (2) $3 W$ (3) $\frac{3 W}{2}$ (4) $\frac{2 W}{3}$ 63. $Assertion (A): Non-polar a materials do not have my permanent dipole moment. Reason (R): When an non-polar material is placed in a electric field, the center of the positive charge distribution of it's individual atom or molecule coinsides with the center of the negative charge distribution. In the light of above statements, choose the most appropriate answer from the options given below.$ (1) $Both (A) and (R) are correct and (R) is the correct explanation of (A).$ (2) $Both (A) and (R) are correct and (R) is not the correct explanation of (A).$ (3) $(A) is correct but (R) is not correct.$ (4) $(A) is not correct but (R) is correct.$ 64. $The Curie temperatures of Cobalt and iron are 1400 K and 1000 K respectively. At T = 1600 K, the ratio of magnetic susceptibility of Cobalt to that of iron is$ (1) $\frac{1}{3}$ (2) $3$ (3) $\frac{7}{5}$ (4) $\frac{5}{7}$ 65. $For protecting a sensitive equipment from the external magnetic field, it should be$ (1) $surrounded with fine copper sheet$ (2) $placed inside an iron can$ (3) $wrapped with insulation around it when passing current through it$ (4) $placed inside an aluminium can$ 66. $At a certain place the angle of dip is 30° and the horizontal component of earth's magnetic field is 0.5 G. The earth's total magnetic field (in G), at that certain place, is:$ (1) $\frac{1}{3}$ (2) $\frac{1}{2}$ (3) $3$ (4) $1$ 67. $For diamagnetic materials, magnetic susceptibility is$ (1) $small and negative$ (2) $small and positive$ (3) $large and negative$ (4) $large and positive$ 68. $A bar magnet is oscillating in the Earth’s magnetic field with a period T. What happens to its period and motion if its mass is quadrupled?$ (1) $motion remains simple harmonic with time period = \frac{T}{2}$ (2) $motion remains S.H.M with time period = 2 T$ (3) $motion remains S.H.M with time period = 4 T$ (4) $motion remains S.H.M and period remains nearly constant$ 69. $A uniform cylindrical rod of length L and radius r, is made from a material whose Young’s modulus of Elasticity equals Y. When this rod is heated by temperature T and simultaneously subjected to a net longitudinal compressional force F, its length remains unchanged. The coefficient of volume expansion, of the material of the rod, is (nearly) equal to:$ (1) $9 F / (π r^{2} YT)$ (2) $6 F / (π r^{2} YT)$ (3) $3 F / (π r^{2} YT)$ (4) $F (3 π r^{2} YT)$ 70. $A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched on, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence the rod gains gravitational potential energy. The work required to do this comes from$ (1) $The current source$ (2) $The magnetic field$ (3) $The lattice structure of the material of the rod$ (4) $The induced electric field due to the changing magnetic field$ 71. $Statement I: The ferromagnetic property depends on temperature. At high temperature, ferromagnet becomes paramagnet. Statement II: At high temperature, the domain wall area of a ferromagnetic substance increases. In the light of the above statements, choose the most appropriate answer from the options given below:$ (1) $Statement I is true but Statement II is false$ (2) $Both Statement I and Statement II are true$ (3) $Both Statement I and Statement II are false$ (4) $Statement I is false but Statement II is true$ 72. $A proton, a deuteron and an α particle are moving with same momentum in a uniform magnetic field. Theratio of magnetic forces action on them is and ______ their speed is_____ in the ratio.$ (1) $2 : 1 : 1 and 4 : 2 : 1$ (2) $1 : 2 : 4 and 2 : 1 : 1$ (3) $1:2:4 and 1 : 1 : 2$ (4) $4 : 2 : 1 and 2 : 1 : 1$ 73. $A susceptibility of a certain magnetic material is 400. What is the class of the magnetic material?$ (1) $Ferromagnetic$ (2) $Diamagnetic$ (3) $Ferroelectric$ (4) $Paramagnetic$ 74. $An electron of mass m and a photon have same energy E . The ratio of wavelength of electron to that of photon is: (c being the velocity of light)$ (1) $\frac{1}{c} (\frac{2 m}{E})^{1/2}$ (2) $\frac{1}{c} (\frac{E}{2 m})^{1/2}$ (3) $(\frac{E}{2 m})^{1/2}$ (4) $c (2 mE)^{1/2}$ 75. $The free space inside a current carrying toroid is filled with a material of susceptibility 2 x 1 0^{- 2} . The percentage increase in the value of magnetic field inside the toroid will be$ (1) $0.2%$ (2) $0.1%$ (3) $2%$ (4) $1%$ 76. $At an angle of 3 0^{0} to the magnetic meridian, the apparent dip is 4 5^{0} . Find the true dip:$ (1) $tan^{- 1} 3$ (2) $tan^{- 1} \frac{1}{3}$ (3) $tan^{- 1} \frac{2}{3}$ (4) $tan^{- 1} \frac{3}{2}$ 77. $In the magnetic meridian of a certain place, the horizontal component of the earth's magnetic field is 86.6 G (Gauss) and the magnetic field of earth is 100 G (Gauss). Then the dip angle is$ (1) $45^{\circ}$ (2) $60^{\circ}$ (3) $30^{\circ}$ (4) $75^{\circ}$ 78. $The relationship between the magnetic susceptibility (x) and the magnetic permeability (μ) is given by: (μ_{0} is the permeability of free space and μ_{T} is relative permeability)$ (1) $X = \frac{μ}{μ _{0}} - 1$ (2) $X = \frac{μ _{r}}{μ _{0}} + 1$ (3) $χ = μ_{r} + 1$ (4) $X = 1 - \frac{μ}{μ _{0}}$ 79. $The horizontal component of Earth's magnetic field at a place is 3 \times 10^{- 5} T . If the dip at that place is 45^{\circ}, the resultant magnetic field at that place is$ (1) $3 \times 10^{- 5} T$ (2) $\frac{3}{2} \times 10^{- 5} T$ (3) $\frac{3}{2} 3 \times 10^{- 5} T$ (4) $32 \times 10^{- 5} T$ 80. $A thin diamagnetic rod is placed vertically between the poles of an electromagnet. When the current in the electromagnet is switched ON, then the diamagnetic rod is pushed up, out of the horizontal magnetic field. Hence, the rod gains gravitational potential energy. The work required to do this comes from [NEET 2018]$ (1) $the lattice structure of the material of the rod$ (2) $the magnetic field$ (3) $the current source$ (4) $the induced electric field due to the changing magnetic field$ 81. $In some ferromagnetic materials magnetization disappears on the removal of the external magnetic field. Such materials are called$ (1) $soft ferromagnetic materials$ (2) $hard ferromagnetic materials$ (3) $anti-ferromagnetic materials$ (4) $semiconductors$ 82. $The magnitude of the axial field due to a short bar magnet at a distance of 50 cm from its mid-point is (The magnetic moment of the bar magnet is 0.4 Am^{2})$ (1) $3.2 \times 10^{- 7} T$ (2) $1.6 \times 10^{- 7} T$ (3) $6.4 \times 10^{- 7} T$ (4) $4.8 \times 10^{- 7} T$ 83. $One of the following substances having the tendency to move from stronger region to the weaker region of the magnetic field is$ (1) $paramagnetic$ (2) $ferromagnetic$ (3) $diamagnetic$ (4) $ferrimagnetic$ 84. $Match the following List-I with List-II. List-I (A) \oint EdA (B) \oint BdA (C) \oint Edl (D) \oint Bdl List-II (I) 0 (II) - \frac{d φ _{B}}{dt} (III) \frac{Q}{ϵ _{0}} (IV) μ_{0} (i_{c} + i_{d})$ (1) $A - (III), B - (II), C - (I), D - (IV)$ (2) $A - (IV), B - (I), C - (III), D - (II)$ (3) $A - (III), B - (I), C - (II), D - (IV)$ (4) $A - (III), B - (I), C - (IV), D - (II)$ 85. $An electron with energy 0.1 keV moves at right angle to the earth's magnetic field of 1 x 1 0^{- 4} W b m^{2} . The frequency of revolution of the electron will be (Take mass of electron = 9.0 x 1 0^{- 31} kg)$ (1) $1.6 x 1 0^{5} Hz$ (2) $5.6 x 1 0^{5} Hz$ (3) $2.8 x 1 0^{6} Hz$ (4) $1.8 x 1 0^{6} Hz$ 86. $Given below are two statements: Statement I: For diamagnetic substance - 1 \leq x < 0, where x is the magnetic susceptibility. Statement II: Diamagnetic substance when placed in an external magnetic field, tend to move from stronger to weaker part of the field. In the light of the above statements, choose the correct answer from the options give below.$ (1) $Both Statement I and Statement II are False$ (2) $Statement I is correct but Statement II is false$ (3) $Statement I is incorrect but Statement II is true$ (4) $Both Statement I and Statement II are true$ 87. $A small bar magnet placed with its axis at 30^{\circ} with an external field of 0.06 T experiences a torque of 0.018 Nm . The minimum work required to rotate it from its stable to unstable equilibrium position is$ (1) $9.2 \times 10^{- 3} J$ (2) $6.4 \times 10^{- 2} J$ (3) $7.2 \times 10^{- 2} J$ (4) $11.7 \times 10^{- 3} J$ 88. $Identify the incorrect statement from the following.$ (1) $The susceptibility of a diamagnetic material is a positive quantity.$ (2) $Paramagnetic materials obey Curie's law.$ (3) $Ferromagnetic materials have permanent magnetic domains.$ (4) $In soft ferromagnetic material, the magnetisation disappear on removal of the external field.$ 89. $For an ideal heat engine, the temperature of the source is 127^{\circ} C . In order to have 60 % efficiency the temperature of the sink should be____^{\circ} C .(Round off to the Nearest Integer) (write modulus or absolute value of the temperature)$ 90. $Two separate wires A and B are stretched by 2 mm and 4 mm respectively, when they are subjected to a force of 2N. Assume that both the wires are made up of same material and the radius of wire B is 4 times that of the radius of wire A. The length of the wires A and B are in the ratio of a : b. Then a/b can be expressed as 1/x where x is$