Magnetism & Matter PYQs Set 2 (PDF)

Set 2 of 6 · Questions 31-60 of 164

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Mere Teacher · Previous Year Questions NEET Physics · Magnetism & Matter · Set 2 (Q31-60)
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31. $A bar magnet is released from rest along the axis of a very long vertical copper tube. After some time the magnet will$ (1) $Move down with an acceleration equal to g$ (2) $Oscillate inside the tube$ (3) $Move down with almost constant speed$ (4) $Move down with an acceleration greater than g$ 32. $A magnetic dipole experiences a torque of 803 N m when placed in uniform magnetic field in such a way that dipole moment makes angle of 60^{\circ} with magnetic field. The potential energy of the dipole is:$ (1) $- 403 J$ (2) $-80 J$ (3) $80 J$ (4) $-60 J$ 33. $Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion (A): Electromagnets are made of soft iron. Reason (R): Soft iron has high permeability and low retentivity. In the light of above statements, choose the most appropriate answer from the options given below.$ (1) $A is not correct but R is correct$ (2) $A is correct but R is not correct$ (3) $Both A and R are correct and R is the correct explanation of A$ (4) $Both A and R are correct but R is not the correct explanation of A$ 34. $The magnetic susceptibility of a paramagnetic material at - 73^{\circ} C is 0.0075 and its value at - 173^{\circ} C will be$ (1) $0.0030$ (2) $0.0075$ (3) $0.0045$ (4) $0.015$ 35. $A uniform conducting wire of length 12a and resistance R is wound up as a current (I) carrying coil in the shape of (A) an equilateral triangle of side a. (B) a square of side a. The magnetic dipole moments of the coil in each case respectively are [NEET 2021]$ (1) $3 I a^{2} and 3 I a^{2}$ (2) $3 I a^{2} and I a^{2}$ (3) $3 I a^{2} and 4 I a^{2}$ (4) $4 I a^{2} and 3 I a^{2}$ 36. $A short bar magnet of magnetic moment 0.4 J T^{1} is placed in a uniform magnetic field of 0.16 T . The magnet is in stable equilibrium when the potential energy is$ (1) $0.0647 J$ (2) $- 0.064 J$ (3) $zero$ (4) $- 0.082 J$ 37. $At a location, the horizontal components of the earth's magnetic field is 0.3 G in the magnetic meridian and the dip angle is 60^{\circ} . The earth's magnetic field at this location in G is$ (1) $0.3$ (2) $0.6$ (3) $0.9$ (4) $1.2$ 38. $A rectangular coil of length 0.12 m and width 0.1 m having 50 turns of wire is suspended vertically in a uniform magnetic field of strength 0.2 Weber / m^{2} . The coil carries a current of 2 A. If the plane of the coil is inclined at an angle of 3 0^{o} with the direction of the field, the torque required to keep the coil in stable equilibrium will be$ (1) $0.24 Nm$ (2) $0.12 Nm$ (3) $0.15 Nm$ (4) $0.20 Nm$ 39. $At a point A on the earth’s surface the angle of dip, δ = + 2 5^{o} . At a point B on the earth’s surface the angle of dip, δ = - 2 5^{o} . We can interpret that$ (1) $A and B are both located in the southern hemisphere.$ (2) $A and B are both located in the northern hemisphere.$ (3) $A is located in the southern hemisphere and B is located in the northern hemisphere.$ (4) $A is located in the northern hemisphere and B is located in the southern hemisphere.$ 40. $If ‘M’ is the mass of water that rises in a capillary tube of radius 'r', then mass of water which will rise in a capillary tube of radius '2r' is:$ (1) $M$ (2) $\frac{M}{2}$ (3) $4 M$ (4) $2 M$ 41. $The magnetic field (B) inside a long solenoid having n turns per unit length and carrying current I when iron core is kept in it is (μ_{0} = permeability of vacuum, χ = magnetic susceptibility)$ (1) $μ_{0} nI (1 - χ)$ (2) $μ_{0} nI χ$ (3) $μ_{0} n I^{2} (1 + χ)$ (4) $μ_{0} nI (1 + χ)$ 42. $A paramagnetic material has 10^{28} atoms / m^{3} . Its magnetic susceptibility at temperature 350 K is 2.8 \times 10^{- 4} . Its suscetibility at 300 K is:$ (1) $3.267 \times 10^{- 4}$ (2) $3.672 \times 10^{- 4}$ (3) $3.726 \times 10^{- 4}$ (4) $2.672 \times 10^{- 4}$ 43. $Ferromagnetic materials used in a transformer must have$ (1) $low permeability and high hysterisis loss$ (2) $high permeability and low hysterisis loss$ (3) $high permeability and high hysterisis loss$ (4) $low permeability and low hysterisis loss.$ 44. $If M_{z} = magnetization of a paramagnetic sample, B = external magnetic field, T = absolute temperature, C = curie constant. Then according to Curie's law in magnetism, the correct relation is$ (1) $M_{z} = \frac{T}{CB}$ (2) $M_{z} = \frac{CB}{T}$ (3) $C = \frac{M _{z} B}{T}$ (4) $C = \frac{T ^{2}}{M _{z} B}$ 45. $Which of the following statement proves that earth has magnetic field?$ (1) $Earth is surrounded by ionosphere.$ (2) $The intensity of cosmic rays stream of charged particles is more as the poles then at the equator.$ (3) $A large quantity of iron-ore is found in the earth.$ (4) $Earth is a planet rotating about the North South axis.$ 46. $At 40° C, a brass wire of 1 mm radius is hung from the ceiling. A small mass, M is hung from the free end of the wire. When the wire is cooled down from 40ºC to 20ºC it regains its original length of 0.2 m. The value of M is close to: (Coefficient of linear expansion and Young’s modulus of brass are 10^{- 5} /° C and 10^{11} N / m^{2}, respectively; g = 10 ms^{- 2})$ (1) $9 kg$ (2) $0.5 kg$ (3) $1.5 kg$ (4) $6.28 kg$ 47. $χ_{1} and χ_{2} are susceptibility of a paramagnetic material at temperatures T_{1} K and T_{2} K respectively, then$ (1) $χ_{1} = χ_{2}$ (2) $χ_{1} T_{1} = χ_{2} T_{2}$ (3) $χ_{1} T_{2} = χ_{2} T_{1}$ (4) $χ_{1} T_{1} = χ_{2} T_{2}$ 48. $A charge q is spread uniformly over an isolated ring of radius R . The ring is rotated about its natural axis with an angular velocity ω . Magnetic dipole moment of the ring is$ (1) $\frac{qω R ^{2}}{2}$ (2) $\frac{qωR}{2}$ (3) $qω R^{2}$ (4) $\frac{qω}{2 R}$ 49. $The magnetic susceptibility of ferromagnetic materials is$ (1) $< 0$ (2) $> 1$ (3) $1$ (4) $0$ 50. $Electromagnets are made of soft iron because soft iron has$ (1) $low retentivity and high coercive force$ (2) $high retentivity and high coercive force$ (3) $low retentivity and low coercive force$ (4) $high retentivity and low coercive force$ 51. $A vibration magnetometer is used at two different places A and B on the earth. The time period of a magnet suspended freely in the magnetometer at A is twice that at B . If the horizontal component of the earth's magnetic field at B is 32 \times 10^{- 6} T, then its value at A is$ (1) $H_{A} = 8 \times 10^{- 6} T$ (2) $H_{A} = 32 \times 10^{- 6} T$ (3) $H_{A} = 4 \times 10^{- 6} T$ (4) $H_{A} = 16 \times 10^{- 6} T$ 52. $Let m and r are the dipole moment and radius of earth respectively. Then, the earth's magnetic field at the equator is$ (1) $\frac{μ _{0} m}{4 π r ^{3}}$ (2) $\frac{μ _{0} m}{8 π r ^{3}}$ (3) $\frac{μ _{0} m}{2 π r ^{3}}$ (4) $\frac{μ _{0} m}{π r ^{3}}$ 53. $The elastic limit of brass is 379 MPa. What should be the minimum diameter of a brass rod if it is to support a 400 N load without exceeding its elastic limit?$ (1) $1.00 mm$ (2) $1.16 mm$ (3) $0.90 mm$ (4) $1.36 mm.$ 54. $Materials suitable for permanent magnets, must have which of the following properties?$ (1) $High retentivity, low coercivity and high permeability.$ (2) $Low retentivity, low coercivity and low permeability.$ (3) $Low retentivity, high coercivity and low permeability.$ (4) $High retentivity, high coercivity and high permeability.$ 55. $The soft-iron is a suitable material for making an electromagnet. This is because soft-iron has:$ (1) $low coercively and high retentively$ (2) $low coercively and low permeability$ (3) $high permeability and low retentively$ (4) $high permeability and high retentively$ 56. $A material of 0.25 cm^{2} cross-sectional area is placed in a magnetic field of strength (H) 1000 Am^{- 1} . Then, the magnetic flux produced is (Susceptibility of material is 313 ) (Permeability of free space, μ_{0} = 4 π \times 10^{- 7} Hm^{- 1})$ (1) $8.33 \times 10^{- 8} Wb$ (2) $1.84 \times 10^{- 6} Wb$ (3) $9.87 \times 10^{- 6} Wb$ (4) $3.16 \times 10^{- 6} Wb$ 57. $Given below are two statements: Statement I: The diamagnetic property depends on temperature Statement II: The induced magnetic dipole moment in a diamagnetic sample is always opposite to the magnetising field In the light of given statements, choose the correct answer from the options given below$ (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) $Both Statement I and Statement II are true$ 58. $A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state. The energy required to rotate it by 60^{\circ} is W. Now the torque required to keep the magnet in this new position is [NEET 2016]$ (1) $\frac{W}{3}$ (2) $3 W$ (3) $\frac{3 W}{2}$ (4) $\frac{2 W}{3}$ 59. $Assertion (A): Non-polar a materials do not have my permanent dipole moment. Reason (R): When an non-polar material is placed in a electric field, the center of the positive charge distribution of it's individual atom or molecule coinsides with the center of the negative charge distribution. In the light of above statements, choose the most appropriate answer from the options given below.$ (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) $(A) is not correct but (R) is correct.$ 60. $The Curie temperatures of Cobalt and iron are 1400 K and 1000 K respectively. At T = 1600 K, the ratio of magnetic susceptibility of Cobalt to that of iron is$ (1) $\frac{1}{3}$ (2) $3$ (3) $\frac{7}{5}$ (4) $\frac{5}{7}$