Magnetism & Matter PYQs Set 6 (PDF)

Set 6 of 6 · Questions 151-176 of 176

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Mere Teacher · Previous Year Questions JEE Main Physics · Magnetism & Matter · Set 6 (Q151-176)
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151. $The percentage increase in magnetic field (b) when space within a current carrying solenoid is filled with magnesium (magnetic susceptibility χ_{M g} = 1.2 \times 1 0^{- 5}) is:$ (1) $\frac{5}{3} \times 1 0^{- 5} %$ (2) $\frac{5}{6} \times 1 0^{- 4} %$ (3) $\frac{5}{6} \times 1 0^{- 5} %$ (4) $\frac{6}{5} \times 1 0^{- 3} %$ 152. $The ratio of magnetic fields due to a bar magnet at the two axial points P_{1} and P_{2}, which are separated from each other by 10 cm is 25 : 2 . Point P_{1} is situated at 10 cm from the centre of the magnet. Magnetic length of the bar magnet is (Points P_{1} and P_{2} are on the same side of magnet and distance of P_{2} from the centre is greater than distance of P_{1} from the centre of magnet)$ (1) $5 cm$ (2) $10 cm$ (3) $15 cm$ (4) $20 cm$ 153. $Which of the following statements are correct? (A) Electric monopoles do not exist whereas magnetic monopoles exist. (B) Magnetic field lines due to a solenoid at it sends and outside cannot be completely straight and confined. (C) Magnetic field lines are completely confined within a toroid. (D) Magnetic field lines inside a bar magnet are not parallel. (E) χ=-1 is the condition for a perfect diamagnetic material, where χ is its magnetic susceptibility. Choose the correct answer from the options given below:$ (1) $(C) and (E) only$ (2) $(B) and (D) only$ (3) $(A) and (B) only$ (4) $(B) and (C) only$ 154. $In order to determine the Young's Modulus of a wire of radius (measured using a scale of least count ) and length (measured using a scale of least count ), a weight of mass (measured using a scale of least count ) was hanged to get the elongation of (measured using ascale of least count ). What will be the fractional error in the value of Young's Modulus determinedby this experiment?$ (1) $0.14 %$ (2) $0.9 %$ (3) $9$ (4) $1.4 %$ 155. $Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).Consider a ferromagnetic material : Assertion (A) : The individual atoms in a ferromagnetic material possess a magnetic dipole moment and interact with one another in such a way that they spontaneously align themselves forming domains. Reason (R): At high enough temperature, the domain structure of ferromagnetic material disintegrates. Thus, magnetization will disappear at high enough temperature known as Curie temperature.In the light of the above statements, choose the correct answer from the options given below :$ (1) $(A) is true but (R) is false$ (2) $Both (A) and (R) are true but (R) is not the correct explanation of (A)$ (3) $(A) is false but (R) is true$ (4) $Both (A) and (R) are true and (R) is the correct explanation of (A)$ 156. $Curie temperature above which$ (1) $paramagnetic material becomes ferromagnetic material$ (2) $ferromagnetic material becomes diamagnetic material$ (3) $ferromagnetic material becomes paramagnetic material$ (4) $paramagnetic material becomes diamagnetic material$ 157. $Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: A bar magnet dropped through a metallic cylindrical pipe takes more time to come down compared to a non-magnetic bar with same geometry and mass. Reason R: For the magnetic bar, Eddy currents are produced in the metallic pipe which oppose the motion of the magnetic bar. In the light of the above statements, choose the correct answer from the options given below$ (1) $A is false but R is true$ (2) $Both A and R are true and R is the correct explanation of A$ (3) $A is true but R is false$ (4) $Both A and R are true and R is NOT the correct explanation of A$ 158. $Two identical thin bar magnets, each of length l and pole strength m, are placed at right angle to each other with north pole of one touching south pole of the other. The magnetic moment of the system is$ (1) $0.5 l m$ (2) $l m$ (3) $21 m$ (4) $2 l m$ 159. $According to Curie’s law, the magnetic susceptibility of a substance at an absolute temperature T is proportional to$ (1) $1/ T$ (2) $T$ (3) $1/ T^{2}$ (4) $T^{2}$ 160. $Choose the correct option:$ (1) $True dip is not mathematically related to apparent dip.$ (2) $True dip is less than apparent dip.$ (3) $True dip is always greater than the apparent dip.$ (4) $True dip is always equal to apparent dip.$ 161. $If χ is the susceptibility and μ_{r} is the relative permeability of a ferromagnetic substance, then$ (1) $χ<<1$ (2) $μ_{r} << 1$ (3) $μ_{r} = 0$ (4) $χ>>1$ 162. $Coercivity of a magnet where the ferromagnet gets completely demagnetized is 3 \times 10^{3} Am^{- 1} . The minimum current required to be passed in a solenoid having 1000 turns per metre, so that the magnet gets completely demagnetized when placed inside the solenoid is$ (1) $3 A$ (2) $30 mA$ (3) $6 A$ (4) $60 mA$ 163. $The magnetic susceptibility is negative for$ (1) $ferromagnetic material only$ (2) $paramagnetic and ferromagnetic materials$ (3) $diamagnetic material only$ (4) $paramagnetic material only$ 164. $The materials suitable for making electromagnets should have$ (1) $high retentivity and high coercivity$ (2) $low retentivity and low coercivity$ (3) $high retentivity and low coercivity$ (4) $low retentivity and high coercivity$ 165. $Which of the following properties is 'False' for a bar magnet?$ (1) $It doesn't produce magnetic field.$ (2) $Its poles cannot be separated.$ (3) $It points in North-South direction when suspended.$ (4) $Its like poles repel and unlike poles attract.$ 166. $A bar magnet of magnetic moment M is placed at right angles to a magnetic induction B . If a force F is experienced by each pole of the magnet, the length of the magnet will be$ (1) $MB / F$ (2) $BF / M$ (3) $MF / B$ (4) $F / MB$ 167. $Paramagnetic substances: (A) align themselves along the directions of external magnetic field.(B) attract strongly towards external magnetic field.(C) has susceptibility little more than zero. (D) move from a region of strong magnetic field to weak magnetic field. Choose the most appropriate answer from the options given below:$ (1) $A, B, C Only$ (2) $A, B, C, D$ (3) $A, C Only$ (4) $B, D Only$ 168. $In a permanent magnet at room temperature$ (1) $domains are partially aligned$ (2) $domains are all perfectly aligned$ (3) $magnetic moment of each molecule is zero$ (4) $the individual molecules have non-zero magnetic moment which are all perfectly aligned.$ 169. $Among which the magnetic susceptibility does not depend on the temperature?$ (1) $diamagnetism$ (2) $paramagnetic$ (3) $ferromagnetism$ (4) $ferrite$ 170. $A soap bubble, blown by a mechanical pump at the mouth of a tube, increases in volume, with time, at a constant rate. The graph that correctly depicts the time dependence of pressure inside the bubble is given by:$ (1) (2) (3) (4) 171. $A diamagnetic material in a magnetic field moves$ (1) $from stronger to the weaker parts of the field$ (2) $from weaker to the stronger parts of the field$ (3) $perpendicular to the field$ (4) $in none of the above directions$ 172. $A bar magnet of length 16 cm is placed in the magnetic meridian with the N -pole pointing towards geographical north. Two neutral points separated by 12 cm are obtained on the equatorial line of the magnet. If the horizontal component of earth's magnetic field = 3.2 \times 10^{- 5} T, then the pole strength of magnet is$ (1) $0.25 Am$ (2) $0.5 Am$ (3) $1 Am$ (4) $2 Am$ 173. $Which of the following do not exist?$ (1) $Electric dipoles$ (2) $Electric monopoles$ (3) $Magnetic monopoles$ (4) $Magnetic dipoles$ 174. $A wire of length 314 cm carrying current of 14 A is bent to form a circle. The magnetic moment of the coil is_______A- m^{2} . [Given π = 3.14]$ 175. $Suppose you have taken a dilute solution of oleic acid in such a way that its concentration becomes 0.01 cm^{3} of oleic acid per cm^{3} of the solution. Then you make a thin film of this solution (monomolecular thickness) of area 4 cm^{2} by considering 100 spherical drops of radius (\frac{3}{40 π})^{\frac{1}{3}} \times 10^{- 3} cm . Then the thickness of oleic acid layer will be x \times 10^{- 14} m . Where x is$ 176. $In a uniform magnetic field, the magnetic needle has a magnetic moment 9.85 \times 1 0^{- 2} A / m^{2} and moment of inertia 5 \times 1 0^{- 6} kg m^{2} . If it performs 10 complete oscillations in 5 seconds then the magnitude of the magnetic field is ___mT [Take π^{2} as 9.85]$