JEE Main & Advanced Physics Magnetism Question Bank

done Self Evaluation Test - Magnetism and Matter Total Questions - 85

• question_answer1)
  If a bar magnet of pole strength m and magnetic moment M is cut perpendicular to its axis in two equal halves then its new pole strength m' and magnetic moment M' are respectively
  A)
  \[m'=m\] and \[M'=M\] done clear
  B)
  \[m'=m\] and \[M'=\frac{M}{2}\] done clear
  C)
  \[m'=\frac{m}{2}\] and \[M'=2M\] done clear
  D)
  \[m'=2m\] and \[M'=\frac{M}{2}\] done clear
  View Solution play_arrow

• question_answer2)
  A curve between magnetic moment and temperature of magnet is    
  A)
  done clear
  B)
  done clear
  C)
    done clear
  D)
  done clear
  View Solution play_arrow

• question_answer3)
  A bar magnet has a length 8 cm. The magnetic field at a point at a distance 3 cm from the centre in the broad side-on position is found to be\[4\times {{10}^{-6}}T\]. The pole strength of the magnet is.
  A)
  \[6\times {{10}^{-5}}Am\] done clear
  B)
  \[5\times {{10}^{-5}}Am\] done clear
  C)
  \[2\times {{10}^{-4}}Am\] done clear
  D)
  \[3\times {{10}^{-4}}Am\] done clear
  View Solution play_arrow

• question_answer4)
  A permanent magnet in the shape of a thin cylinder of length \[10\text{ }cm\] has magnetization \[(M)={{10}^{6}}\,A\,{{m}^{-1}}\]. Its magnetization current\[{{I}_{M}}\]is
  A)
  \[{{10}^{5}}\,A\] done clear
  B)
  \[{{10}^{6}}\,A\] done clear
  C)
  \[{{10}^{7}}\,A\] done clear
  D)
  \[{{10}^{8}}\,A\] done clear
  View Solution play_arrow

• question_answer5)
  Assume that each iron atom has a permanent magnetic moment equal to 2 Bohr magnetrons (1 Bohr magnetos \[=9.27\times {{10}^{-24}}\,A-{{m}^{2}}\]). The density of atoms in iron is \[8.52\times {{10}^{28}}\,atoms/{{m}^{3}}.\]Find the maximum magnetic moment per unit volume.
  A)
  \[1.5\times {{10}^{2}}\,A/m\] done clear
  B)
  \[1.58\times {{10}^{6}}\,A/m\] done clear
  C)
  \[1.2\times {{10}^{5}}\,A/m\] done clear
  D)
  \[1.3\times {{10}^{6}}\,A/m\] done clear
  View Solution play_arrow

• question_answer6)
  A bar magnet of magnetic moment \[4.0\,A-{{m}^{2}}\] is free to rotate about a vertical axis through its center. The magnet is released from rest from east-west position. Kinetic energy of the magnet in north-south position will be \[(H=25\mu T)\]
  A)
  \[{{10}^{-2}}J\] done clear
  B)
  \[{{10}^{-4}}J\] done clear
  C)
  \[{{10}^{-6}}J\] done clear
  D)
  0 done clear
  View Solution play_arrow

• question_answer7)
  A short bar magnet of magnetic moment \[0.4J\,{{T}^{-1}}\] is placed in a uniform magnetic field of\[0.16\,T\]. The magnet is in stable equilibrium when the potential energy is
  A)
  \[-0.64J\] done clear
  B)
  zero  done clear
  C)
  \[-0.082\,J\] done clear
  D)
  \[0.064\,J\] done clear
  View Solution play_arrow

• question_answer8)
  A coil in the shape of an equilateral triangle of side l is suspended between the pole pieces of a permanent magnet such that \[\vec{B}\] is in plane of the coil. If due to a current i in the triangle a torque \[\tau \] acts on it, the side l of the triangle is            
  A)
  \[\frac{2}{\sqrt{3}}{{\left( \frac{\tau }{B.i} \right)}^{\frac{1}{2}}}\] done clear
  B)
  \[2{{\left( \frac{\tau }{\sqrt{3}B.i} \right)}^{\frac{1}{2}}}\] done clear
  C)
  \[\frac{2}{\sqrt{3}}\left( \frac{\tau }{B.i} \right)\] done clear
  D)
  \[\frac{1}{\sqrt{3}}\frac{\tau }{B.i}\] done clear
  View Solution play_arrow

• question_answer9)
  A bar magnet of magnetic moment \[3.0\,A-{{m}^{2}}\] is placed in a uniform magnetic field of \[2\times {{10}^{-5}}T\].If each pole of the magnet experiences a force of \[6\times {{10}^{-4}}N\], the length of the magnet is
  A)
  0.5 m done clear
  B)
  0.3 m done clear
  C)
   0.2 m done clear
  D)
  0.1 m done clear
  View Solution play_arrow

• question_answer10)
  The net magnetic moment of two identical magnets each of magnetic moment \[{{M}_{0}}\], inclined at \[60{}^\circ \] with each other is
  A)
  \[{{M}_{0}}\]   done clear
  B)
  \[\sqrt{2}\,{{M}_{0}}\] done clear
  C)
  \[\sqrt{3}\,{{M}_{0}}\]  done clear
  D)
  \[2{{M}_{0}}\] done clear
  View Solution play_arrow

• question_answer11)
  Two identical magnetic dipoles of magnetic moments\[1.0\,A\,-{{m}^{2}}\], each, placed at a separation of 2m with their axis perpendicular to each other. The resultant magnetic field at a point midway between the dipoles is
  A)
  \[5\times {{10}^{-7}}\,T\] done clear
  B)
  \[\sqrt{5}\times {{10}^{-7}}\,T\] done clear
  C)
  \[{{10}^{-7}}\,T\] done clear
  D)
  None of these done clear
  View Solution play_arrow

• question_answer12)
  A magnetic needle is kept in a non-uniform magnetic field. It experiences
  A)
  neither a force nor a torque done clear
  B)
  a torque but not a force done clear
  C)
  a force but not a torque done clear
  D)
  a force and a torque done clear
  View Solution play_arrow

• question_answer13)
  Force between two identical bar magnets whose centres are r metre apart is 4.8 N, when their axes are in the same line. If separation is increased to r, the force between them is
  A)
  2.4 N done clear
  B)
  1.2N done clear
  C)
  0.6 N done clear
  D)
  0.3 N done clear
  View Solution play_arrow

• question_answer14)
  A magnetic needle lying parallel to a magnetic field requires W units of work to turn it through\[60{}^\circ \]. The torque required to maintain the needle in this position will be
  A)
  \[\sqrt{3}W\] done clear
  B)
  W     done clear
  C)
  \[\frac{\sqrt{3}}{2}W\] done clear
  D)
   2W done clear
  View Solution play_arrow

• question_answer15)
  A uniform magnetic field parallel to the plane of the paper exists in space initially directed from left to right. When a bar of soft iron is placed in the field parallel to it, the lines of force passing through it will be represented by
  A)
  done clear
  B)
  done clear
  C)
  done clear
  D)
  done clear
  View Solution play_arrow

• question_answer16)
  A bar magnet having centre 0 has a length of 4 cm. Point \[{{P}_{1}}\]is in the broad side-on and \[{{P}_{2}}\] is in the end side-on position with \[O{{P}_{1}}=O{{P}_{2}}=10\] metres. The ratio of magnetic intensities H at \[{{P}_{1}}\] and \[{{P}_{2}}\]is
  A)
  \[{{H}_{1}}:{{H}_{2}}=16:100\] done clear
  B)
  \[{{H}_{1}}:{{H}_{2}}=1:2\] done clear
  C)
  \[{{H}_{1}}:{{H}_{2}}=2:1\] done clear
  D)
  \[{{H}_{1}}:{{H}_{2}}=100:16\] done clear
  View Solution play_arrow

• question_answer17)
  The mid points of two small magnetic dipoles of length d in end-on positions, are separated by a distance x, (x>>d). The force between them is proportional to \[{{x}^{-n}}\] where n is:
  A)
  1 done clear
  B)
  2      done clear
  C)
  3 done clear
  D)
  4 done clear
  View Solution play_arrow

• question_answer18)
  A bar magnet of length \['\ell '\] and magnetic dipole moment ?M? is bent in the form of an are as shown in figure. The new magnetic dipole moment will be 
  A)
  \[\frac{3}{\pi }M\] done clear
  B)
  \[\frac{2}{\pi }M\] done clear
  C)
  \[\frac{M}{2}\] done clear
  D)
  M done clear
  View Solution play_arrow

• question_answer19)
  Two isolated point poles of strength 30 A-m and 60 A-m are placed at a distance of 0.3m. The force of repulsion is                           
  A)
  \[2\times {{10}^{-3}}N\]           done clear
  B)
  \[2\times {{10}^{-4}}N\] done clear
  C)
  \[2\times {{10}^{5}}N\]        done clear
  D)
         \[2\times {{10}^{-5}}N\] done clear
  View Solution play_arrow

• question_answer20)
  A magnet of magnetic moment \[50\hat{i}\,\,A-{{m}^{2}}\]is placed along the x-axis in a magnetic field\[\overset{\to }{\mathop{B}}\,=(0.5\hat{i}+3.0\hat{j})T\]. The torque acting on the magnet is
  A)
  \[175\,\hat{k}\,N-m\]      done clear
  B)
         \[150\,\hat{k}\,N-m\] done clear
  C)
  \[75\,\hat{k}\,N-m\]       done clear
  D)
         \[25\sqrt{37}\,\hat{k}\,\,N-m\] done clear
  View Solution play_arrow

• question_answer21)
  A magnetic dipole is under the influence of two magnetic fields. The angle between the field directions is \[60{}^\circ \] and one of the fields has a magnitude of \[1.2\times {{10}^{-2}}T\]. If the dipole comes to stable equilibrium at an angle of \[15{}^\circ \] with this field, what is the magnitude of other field?
  A)
  \[4.4\times {{10}^{-3}}\,tesla\] done clear
  B)
  \[5.2\times {{10}^{-3}}\,tesla\] done clear
  C)
  \[3.4\times {{10}^{-3}}\,tesla\] done clear
  D)
  \[7.8\times {{10}^{-3}}\,tesla\] done clear
  View Solution play_arrow

• question_answer22)
  Two short bar magnets P and Q are arranged such that their centres are on the X-axis and are separated by a large distance. The magnetic axes of P and Q are along X and Y axes respectively. At a point R, midway between their centres, if B is the magnitude of induction due to Q, the magnitude of total induction at R due to the both magnets is
  A)
  3B done clear
  B)
  \[\sqrt{5}B\] done clear
  C)
  \[\frac{\sqrt{5}}{2}B\] done clear
  D)
  \[B\] done clear
  View Solution play_arrow

• question_answer23)
  A circular coil of 16 turns and radius 10cm carries a current of 0.75 A and rest with its plane normal to an external magnetic field of \[5.0\times {{10}^{-2}}T\]. The coil is free to rotate about its stable equilibrium position with a frequency of \[2.0\,{{s}^{-1}}\] Compute the moment of inertia of the coil about its axis of rotation.                 
  A)
  \[3.4\times {{10}^{-5}}\,kg\,{{m}^{2}}\]  done clear
  B)
  \[1.2\times {{10}^{-4}}\,kg\,{{m}^{2}}\] done clear
  C)
  \[2.6\times {{10}^{-4}}\,kg\,{{m}^{2}}\]   done clear
  D)
         \[4.7\times {{10}^{-5}}\,kg\,{{m}^{2}}\] done clear
  View Solution play_arrow

• question_answer24)
  The figure below shows the north and south poles of a permanent magnet in which n turn coil of area of cross-section A is resting, such that for a current i passed through the coil, the plane of the coil makes an angle \[\theta \] with respect to the direction of magnetic field B. If the plane of the magnetic field and the coil are horizontal and vertical respectively, the torque on the coil will be
  A)
  \[\tau =niAB\,\cos \theta \] done clear
  B)
         \[\tau =niAB\,\sin \theta \] done clear
  C)
  \[\tau =niAB\,\]  done clear
  D)
  None of the above, since the magnetic field is radial. done clear
  View Solution play_arrow

• question_answer25)
  A magnetic dipole is acted upon by two magnetic Fields which are inclined to each other at an angle of \[{{75}^{o}}\]. One of the fields has a magnitude of 15 mT. The dipole attains stable equilibrium at an angle of \[{{30}^{o}}\]with this field. The magnitude of the other field (in mT) is close to:
  A)
  1 done clear
  B)
  11 done clear
  C)
  36 done clear
  D)
  1060 done clear
  View Solution play_arrow

• question_answer26)
  A 25 cm long solenoid has radius 2 cm and 500 total number of turns. It carries a current of 15A. If it is equivalent to a magnet of the same size and magnetization \[\vec{M}\] (magnetic moment/volume), then \[\left| \left. {\vec{M}} \right| \right.\] is:
  A)
  \[30000\pi \,A{{m}^{-1}}\]       done clear
  B)
  \[3\pi \,A{{m}^{-1}}\] done clear
  C)
  \[30000\,A{{m}^{-1}}\]            done clear
  D)
  \[300\,A{{m}^{-1}}\] done clear
  View Solution play_arrow

• question_answer27)
  A magnet of magnetic moment M is rotated through \[{{360}^{o}}\] in a magnetic field H, the work done will be
  A)
  \[MH\]   done clear
  B)
  \[2MH\] done clear
  C)
  \[2\pi MH\]         done clear
  D)
  Zero done clear
  View Solution play_arrow

• question_answer28)
  A steel wire of length \[\ell \] has a magnetic moment M. It is bent in L-shape. The new magnetic moment is
  A)
  M         done clear
  B)
  \[\frac{M}{\sqrt{2}}\] done clear
  C)
  \[\frac{M}{2}\]  done clear
  D)
  \[2M\] done clear
  View Solution play_arrow

• question_answer29)
  A bar magnet having a magnetic moment of \[2\times {{10}^{4}}J{{T}^{-1}}\] is free to rotate in a horizontal plane. A horizontal magnetic field \[B=6\times {{10}^{-4}}T\] exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction \[60{}^\circ \] from the field is
  A)
  12 J      done clear
  B)
  6 J done clear
  C)
  2 J        done clear
  D)
  0.6 J done clear
  View Solution play_arrow

• question_answer30)
  Two identical short bar magnets, each having magnetic moment of \[10\,A{{m}^{2}}\], are arranged such that their axial lines are perpendicular to each other and their centres be along the same straight line in a horizontal plane. If the distance between their centres is 0.2 m, the resultant magnetic induction at a point midway between them is \[({{\mu }_{0}}=4\pi \times {{10}^{-7}}\,H{{m}^{-1}})\]
  A)
  \[\sqrt{2}\times {{10}^{-7}}\,tesla\] done clear
  B)
  \[\sqrt{5}\times {{10}^{-7}}\,tesla\] done clear
  C)
  \[\sqrt{2}\times {{10}^{-3}}\,tesla\] done clear
  D)
  \[\sqrt{5}\times {{10}^{-3}}\,tesla\] done clear
  View Solution play_arrow

• question_answer31)
  If the angular momentum of an electron is \[\vec{J}\] then the magnitude of the magnetic moment will be
  A)
  \[\frac{eJ}{m}\] done clear
  B)
  \[\frac{eJ}{2m}\] done clear
  C)
  \[eJ\,2m\]           done clear
  D)
  \[\frac{2m}{eJ}\]           done clear
  View Solution play_arrow

• question_answer32)
  The strength of the earth?s magnetic field is
  A)
  constant everywhere        done clear
  B)
  zero everywhere done clear
  C)
  having very high value done clear
  D)
  vary from place to place on the earth?s surface done clear
  View Solution play_arrow

• question_answer33)
  Which of the following is responsible for the earth?s magnetic field?
  A)
  convective currents in earth?s core. done clear
  B)
  Diversive current in earth?s core. done clear
  C)
  Rotational motion of earth. done clear
  D)
  Translational motion of earth. done clear
  View Solution play_arrow

• question_answer34)
  One can define'..A'. of a place as the vertical plane which passes through the imaginary line joining the magnetic North and the south-poles. Here, A refers to
  A)
  geographic meridian done clear
  B)
  magnetic meridian done clear
  C)
  magnetic declination done clear
  D)
  magnetic inclination done clear
  View Solution play_arrow

• question_answer35)
  At a place, if the earth?s horizontal and vertical components of magnetic fields are equal, then the angle of dip will be
  A)
  \[30{}^\circ \]   done clear
  B)
  \[90{}^\circ \] done clear
  C)
  \[45{}^\circ \] done clear
  D)
  \[0{}^\circ \] done clear
  View Solution play_arrow

• question_answer36)
  The earth?s magnetic field lines resemble that of a dipole at centre of the earth. If the magnetic moment of this dipole is close to\[8\times {{10}^{22}}A{{m}^{2}}\], the value of earth?s magnetic field near the equator is close to (radius of the earth \[=6.4\times {{10}^{6}}m\])
  A)
  0.6 Gauss done clear
  B)
  1.2 Gauss done clear
  C)
  1.8 Gauss done clear
  D)
  0.32 Gauss done clear
  View Solution play_arrow

• question_answer37)
  The magnetic field of earth at the equator i approximately \[4\times {{10}^{-5}}T\]. The radius of earth is\[6.4\times {{10}^{6}}m\]. Then the dipole moment of the earth will be nearly of the order of:
  A)
  \[{{10}^{23}}\,A\,m\] done clear
  B)
  \[{{10}^{20}}\,A\,{{m}^{2}}\] done clear
  C)
  \[{{10}^{16}}\,A\,{{m}^{2}}\] done clear
  D)
  \[{{10}^{10}}\,A\,{{m}^{2}}\] done clear
  View Solution play_arrow

• question_answer38)
  Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moments is
  A)
  4 : 9 done clear
  B)
  9 : 4 done clear
  C)
  2 : 3 done clear
  D)
  3 : 2 done clear
  View Solution play_arrow

• question_answer39)
  Time periods of vibation of two bar magnets in sum and difference positions are 4 sec and 6 sec respectively. The ratio of their magnetic moments \[{{M}_{1}}/{{M}_{2}}\]is          
  A)
  6 : 4  done clear
  B)
  30 : 16 done clear
  C)
  2.6 : 1 done clear
  D)
  1.5 : 1 done clear
  View Solution play_arrow

• question_answer40)
  A compass needle whose magnetic moment is\[60\,A{{m}^{2}}\], is directed towards geographical north at any place experiencing moment of force of\[1.2\times {{10}^{-3}}Nm\]. At that place the horizontal component of earth field is 40 micro\[W/{{m}^{2}}\]. What is the value of dip angle at that place?
  A)
  \[30{}^\circ \] done clear
  B)
  \[60{}^\circ \]   done clear
  C)
  \[45{}^\circ \] done clear
  D)
  \[15{}^\circ \] done clear
  View Solution play_arrow

• question_answer41)
  A dip needle lies initially in the magnetic meridian when it shows an angle of dip \[\theta \] at a place. The dip circle is rotated through an angle x in the horizontal plane and then it shows an angle of dip\[\theta \]. Then \[\frac{\tan \,\theta '}{\tan \,\theta }\]is
  A)
  \[\frac{1}{\cos \,x}\] done clear
  B)
  \[\frac{1}{\sin \,x}\] done clear
  C)
  \[\frac{1}{\tan \,x}\] done clear
  D)
  \[\cos \,x\] done clear
  View Solution play_arrow

• question_answer42)
  A dip circle is so set that its needle moves freely in the magnetic meridian. In this position, the angle of dip is \[40{}^\circ \]. Now the dip circle is rotated so that the plane in which the needle moves makes an angle of \[30{}^\circ \] with the magnetic meridian. In this position, the needle will dip by an angle
  A)
  \[{{40}^{o}}\] done clear
  B)
  \[30{}^\circ \] done clear
  C)
  more than \[40{}^\circ \] done clear
  D)
  less than \[{{40}^{o}}\] done clear
  View Solution play_arrow

• question_answer43)
  A compass needle placed at a distance r from a short magnet in Tan A position shows a deflection of \[60{}^\circ \]. If the distance is increased to r \[{{(3)}^{1/3}}\], then deflection of compass needle is
  A)
  \[{{30}^{o}}\] done clear
  B)
  \[60\times {{3}^{\frac{1}{3}}}\] done clear
  C)
  \[60\times {{3}^{\frac{2}{3}}}\] done clear
  D)
  \[60\times {{3}^{\frac{3}{3}}}\] done clear
  View Solution play_arrow

• question_answer44)
  The radius of the coil of a tangent galvanometer is 16cm. How many turns of the wire should be used if a current of 40m A is to produced at deflection of \[45{}^\circ \]. given, horizontal component of earth's field is \[0.36\times {{10}^{-4}}T\].
  A)
  458 done clear
  B)
  229   done clear
  C)
  200 done clear
  D)
  115 done clear
  View Solution play_arrow

• question_answer45)
  A bar magnet 8 cms long is placed in the magnetic merdian with the N-pole pointing towards geographical north. Two netural points separated by a distance of 6 cms are obtained on the equatorial axis of the magnet. If horizontal component of earth's field \[=3.2\times {{10}^{-5}}T\], then pole strength of magnet is    
  A)
  \[5\,ab-amp\times cm\] done clear
  B)
  \[10\,ab-amp\times cm\] done clear
  C)
  \[2.5\,ab-amp\times cm\] done clear
  D)
  \[20\,ab-amp\times cm\] done clear
  View Solution play_arrow

• question_answer46)
  The length of a magnet is large compared to its width and breadth. The time period of its oscillation in a vibration magnetometer is 2 s. The magnet is cut along its length into three equal parts and three parts are then placed on each other with their like poles together. The time period of this combination will be    
  A)
  2s                     done clear
  B)
                     \[2/3s\] done clear
  C)
              \[2\sqrt{3\,}s\] done clear
  D)
                                 \[2/\sqrt{3\,}s\] done clear
  View Solution play_arrow

• question_answer47)
  The true value of angle of dip at a place is \[60{}^\circ \], the apparent dip in a plane inclined at an angle of \[30{}^\circ \] with magnetic meridian is
  A)
   \[{{\tan }^{-1}}\frac{1}{2}\]   done clear
  B)
   \[{{\tan }^{-1}}(2)\] done clear
  C)
  \[{{\tan }^{-1}}\left( \frac{2}{3} \right)\]    done clear
  D)
   \[{{\tan }^{-1}}\left( \frac{\sqrt{3}}{4} \right)\] done clear
  View Solution play_arrow

• question_answer48)
  Let V and H be the vertical and horizontal components of earth's magnetic field at any point on earth. Near the North Pole
  A)
  V>>H  done clear
  B)
  V<<H done clear
  C)
  V=H done clear
  D)
  V=H=0 done clear
  View Solution play_arrow

• question_answer49)
  A torque of \[{{10}^{-\,5}}\,Nm\] is required to hold a magnet at \[90{}^\circ \] with the horizontal component H of the earth's magnetic field. The torque to hold it at \[30{}^\circ \] will be
  A)
  \[5\times {{10}^{-6}}\,Nm\] done clear
  B)
  5 Nm done clear
  C)
  \[\frac{1}{3}\times {{10}^{-5}}\,Nm\] done clear
  D)
  \[5\sqrt{3}\times {{10}^{-6}}\,Nm\] done clear
  View Solution play_arrow

• question_answer50)
  A tangent galvanometer is connected directly to an ideal battery. If the number of turns in the coil is doubled, the deflection will 
  A)
  increase done clear
  B)
  decrease done clear
  C)
  remain same done clear
  D)
  any of these done clear
  View Solution play_arrow

• question_answer51)
  The magnetic needle of a tangent galvanometer is deflected at an angle \[30{}^\circ \] due to a magnet. The horizontal component of earth's magnetic field \[0.34\times {{10}^{-4}}\,T\] is along the plane of the coil. The magnetic intensity is
  A)
  \[1.96\times {{10}^{-4}}\,T\] done clear
  B)
  \[1.96\times {{10}^{-5}}\,T\] done clear
  C)
  \[1.96\times {{10}^{4}}\,T\] done clear
  D)
  \[1.96\times {{10}^{5}}\,T\] done clear
  View Solution play_arrow

• question_answer52)
  A 10 cm long bar magnet of magnetic moment \[1.34\,A{{m}^{2}}\] is placed in the magnetic meridian with its south pole pointing geographical south. The neutral point is obtained at a distance of 15 cm from the centre of the magnet. Calculate the horizontal component of earth's magnetic field.
  A)
  \[0.12\times {{10}^{-4}}\,T\]     done clear
  B)
         \[0.21\times {{10}^{-4}}T\] done clear
  C)
  \[0.34\times {{10}^{-4}}T\]       done clear
  D)
  \[0.87\times {{10}^{-7}}T\] done clear
  View Solution play_arrow

• question_answer53)
  A short bar magnet is placed in the magnetic meridian of the earth with North Pole pointing north. Neutral points are found at a distance of 30 cm from the magnet on the East-West line, drawn through the middle point of the magnet. The magnetic moment of the magnet in \[A{{m}^{2}}\] is close to: (Given \[\frac{{{\mu }_{0}}}{4\pi }={{10}^{-7}}\] in SI units and \[{{B}_{H}}\]=Horizontal component of earth's magnetic field \[=3.6\times {{10}^{-5}}\,tesla\])
  A)
  14.6  done clear
  B)
  19.4   done clear
  C)
  9.7  done clear
  D)
  4.9 done clear
  View Solution play_arrow

• question_answer54)
  At a place on earth, horizontal component of earth's magnetic field is \[{{B}_{1}}\] and vertical component of earth's magnetic field is \[{{B}_{2}}\]. If a magnetic needle is kept vertical, in a plane making angle \[\alpha \] with the horizontal component of magnetic field, then square of time period of oscillation of needle when slightly distributed is proportional to
  A)
  \[\frac{1}{\sqrt{{{B}_{1}}\,\cos \,\alpha }}\] done clear
  B)
  \[\frac{1}{\sqrt{{{B}_{2}}}}\] done clear
  C)
  \[\frac{1}{\sqrt{{{({{B}_{1\,}}\cos \,\alpha )}^{2}}+B_{2}^{2}}}\] done clear
  D)
  infinite done clear
  View Solution play_arrow

• question_answer55)
  A long straight horizontal cable carries a current of 2.5 A in the direction \[10{}^\circ \] south of west to \[10{}^\circ \] north of east. The magnetic meridian of the place happens to be \[10{}^\circ \] west of the geographic meridian. The earth's magnetic field at the location is 0.33 Gauss, and the angle of dip is zero. Locate the line of neutral points. (Ignore the thickness of the cable).
  A)
  1.5 cm done clear
  B)
  2.5 cm done clear
  C)
  3.5 cm done clear
  D)
  2.0 cm done clear
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• question_answer56)
  The time period of oscillation of a bar magnet suspended horizontally along the magnetic meridian is \[{{T}_{0}}\]. If this magnet is replaced by another magnet of the same size and pole strength but with double the mass, the new time period will be
  A)
  \[\frac{{{T}_{0}}}{2}\]   done clear
  B)
  \[\frac{{{T}_{0}}}{\sqrt{2}}\]   done clear
  C)
  \[\sqrt{2}{{T}_{0}}\] done clear
  D)
  \[2{{T}_{0}}\] done clear
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• question_answer57)
  A magnet makes 40 oscillations per minute at a place having magnetic field intensity of\[0.1\times {{10}^{-5}}\,T\]. At another place, it takes 2.5 sec to complete one vibration. The value of earth's horizontal field at that place is
  A)
  \[0.25\times {{10}^{-6}}\,T\] done clear
  B)
  \[0.36\times {{10}^{-6}}\,T\] done clear
  C)
  \[0.66\times {{10}^{-8}}\,T\] done clear
  D)
  \[1.2\times {{10}^{-6}}\,T\] done clear
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• question_answer58)
  Two short magnets with their axes horizontal and perpendicular to the magnetic maridian are placed with their centres 40 cm east and 50 cm west of magnetic needle. If the needle remains undeflected, the ratio of their magnetic moments \[{{M}_{1}}:{{M}_{2}}\]is                
  A)
  4 : 5 done clear
  B)
  16 : 25 done clear
  C)
  64 : 125 done clear
  D)
  \[2:\sqrt{5}\] done clear
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• question_answer59)
  A current carrying coil is placed with its axis perpendicular to N-S direction. Let horizontal component of earth's magnetic field be \[{{H}_{0}}\] and magnetic field inside the loop be H. If a magnet is suspended inside the loop, it makes angle \[\theta \] with H. Then \[\theta \]=
  A)
  \[{{\tan }^{-1}}\left( \frac{{{H}_{0}}}{H} \right)\] done clear
  B)
  \[{{\tan }^{-1}}\left( \frac{H}{{{H}_{0}}} \right)\] done clear
  C)
  \[\cos e{{c}^{-1}}\left( \frac{H}{{{H}_{0}}} \right)\] done clear
  D)
  \[{{\cot }^{-1}}\left( \frac{{{H}_{0}}}{H} \right)\] done clear
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• question_answer60)
  A 30 cm long bar magnet is placed in the magnetic meridian with its north pole pointing south. The neutral point is obtained at a distance of 40cm from the center of the magnet. Find the pole strength of the magnet. The horizontal component of earth's magnetic field is 0.34 gauss.
  A)
  25.7 Am done clear
  B)
  23.7 Am  done clear
  C)
  28.7 Am done clear
  D)
  26.7 Am  done clear
  View Solution play_arrow

• question_answer61)
  A freely suspended magnet oscillates with period T in earth's horizontal magnetic field. When a bar magnet is brought near it, such that the magnetic field created by bar magnet is in same direction as earth's horizontal magnetic field, the period decreases to T/2. The ratio of the field of the magnet F to the earth's magnetic field (H) is
  A)
  1 : 3      done clear
  B)
  1 : 1   done clear
  C)
  3 : 1      done clear
  D)
  9 : 1 done clear
  View Solution play_arrow

• question_answer62)
  A compass which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It
  A)
  will stay in north-south direction only done clear
  B)
  will stay in east-west direction only done clear
  C)
  will stay in any position done clear
  D)
  None of these done clear
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• question_answer63)
  A very small magnet is placed in the magnetic meridian with its south pole pointing north. The null point is obtained 20 cm away from the centre of the magnet. If the earth's magnetic field (horizontal component) at this point be 0.3 gauss, the magnetic moment of the magnet is
  A)
  \[8.0\times {{10}^{2}}\,e.m.u.\] done clear
  B)
  \[1.2\times {{10}^{3}}\,e.m.u.\] done clear
  C)
  \[2.4\times {{10}^{3}}\,e.m.u.\] done clear
  D)
  \[3.6\times {{10}^{3}}\,e.m.u.\] done clear
  View Solution play_arrow

• question_answer64)
  In end on and broadside on position of a deflection magnetometer, if \[{{\theta }_{1}}\] and \[{{\theta }_{2}}\] are the deflections produced by short magnets at equal distances, then \[\tan \,{{\theta }_{1}}/\tan {{\theta }_{2}}\] is
  A)
  2 : 1 done clear
  B)
  1 : 2  done clear
  C)
  1 : 1 done clear
  D)
  4 : 1 done clear
  View Solution play_arrow

• question_answer65)
  The magnetic needle has magnetic moment \[8.7\times {{10}^{-2}}\,A{{m}^{2}}\] and moment of inertia\[11.5\times {{10}^{-6}}\,kg{{m}^{2}}\]. It performs 10 complete oscillations in 6.70 s, what is the magnitude of the magnetic field?
  A)
  0.012 T done clear
  B)
  0.120 T    done clear
  C)
  1.200 T done clear
  D)
  2.10 T     done clear
  View Solution play_arrow

• question_answer66)
  If the period of oscillation of freely suspended bar magnet in earth's horizontal field H is 4 sec. When another magnet is brought near it, the period of oscillation is reduced to 2s. The magnetic field of second bar magnet is
  A)
  4H   done clear
  B)
  3H   done clear
  C)
  2H   done clear
  D)
  \[\sqrt{3}H\] done clear
  View Solution play_arrow

• question_answer67)
  A vibration magnetometer consists of two identical bar magnets placed one over the other such that they are perpendicular and bisect each other. The time period of oscillation in a horizontal magnetic field is\[{{2}^{5/4}}\]seconds. One of the magnets is removed and if the other magnet oscillates in the same field, then the time period in seconds is
  A)
  \[{{2}^{1/4}}\]  done clear
  B)
  \[{{2}^{1/2}}\] done clear
  C)
  2   done clear
  D)
  \[{{2}^{3/4}}\] done clear
  View Solution play_arrow

• question_answer68)
  The graph between\[\chi \]and 1/T for paramagnetic material will be represented by
  A)
  done clear
  B)
  done clear
  C)
  done clear
  D)
  done clear
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• question_answer69)
  The B - H curve (i) and (ii) shown in fig associated with
  A)
  (i) diamagnetic and (ii) paramagnetic substance      done clear
  B)
  (i) paramagnetic and (ii) ferromagnetic substance     done clear
  C)
  (i) soft iron and (ii) steel     done clear
  D)
  (i) steel and (ii) soft iron done clear
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• question_answer70)
  The magnetic susceptibility of a paramagnetic substances at \[-73{}^\circ \,C\]is 0.0060, then its value at -\[173{}^\circ C\] will be
  A)
  0.0030 done clear
  B)
  0.0120 done clear
  C)
  0.0180 done clear
  D)
  0.0045 done clear
  View Solution play_arrow

• question_answer71)
  Relative permeability of iron is 5500, then its mangetic susceptibility will be
  A)
  5501 done clear
  B)
  5499 done clear
  C)
  \[5500\times {{10}^{7}}\] done clear
  D)
  None of these done clear
  View Solution play_arrow

• question_answer72)
  Relative permittivity and permeability of a material \[{{\varepsilon }_{r}}\] and \[{{\mu }_{r}}\], respectively. Which of the following values of these quantities are allowed for a diamagnetic material?
  A)
  \[{{\varepsilon }_{r}}=0.5,\,\,\,{{\mu }_{r}}=1.5\] done clear
  B)
  \[{{\varepsilon }_{r}}=1.5,\,\,\,{{\mu }_{r}}=0.5\] done clear
  C)
  \[{{\varepsilon }_{r}}=0.5,\,\,\,{{\mu }_{r}}=0.5\] done clear
  D)
  \[{{\varepsilon }_{r}}=1.5,\,\,\,{{\mu }_{r}}=1.5\] done clear
  View Solution play_arrow

• question_answer73)
  A magnetising field of\[2\times {{10}^{3}}\,amp/m\] produces a magnetic flux density of \[8\pi \,\,Tesla\] in an iron rod. The relative permeability of the rod will be -
  A)
  \[{{10}^{2}}\]   done clear
  B)
  \[{{10}^{0}}\]  done clear
  C)
  \[{{10}^{4}}\]  done clear
  D)
  \[{{10}^{1}}\] done clear
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• question_answer74)
  At a temperatur of \[30{}^\circ C\], the susceptibility of a ferromagnetic material is found to be X. Its susceptibility at \[333{}^\circ C\] is
  A)
  \[\chi \]  done clear
  B)
  \[0.5\chi \] done clear
  C)
  \[2\chi \]   done clear
  D)
  \[11.1\chi \] done clear
  View Solution play_arrow

• question_answer75)
  A watch glass containing some powdered substance is placed between the pole pieces of a magnet. Deep concavity is observed at the centre. The substance in the watch glass is
  A)
  iron  done clear
  B)
  chromium done clear
  C)
  carbon done clear
  D)
  wood done clear
  View Solution play_arrow

• question_answer76)
  A permanent magnet in the shape of a thin cylinder of length 10 cm has magnetisation (M) \[={{10}^{6}}\,A\,{{m}^{-1}}\]. Its magnetization current\[{{I}_{M}}\]is
  A)
  \[{{10}^{5}}\,A\] done clear
  B)
  \[{{10}^{6}}\,A\] done clear
  C)
  \[{{10}^{7}}\,A\] done clear
  D)
  \[{{10}^{8}}\,A\] done clear
  View Solution play_arrow

• question_answer77)
  If the magnetic dipole moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are denoted by\[{{\mu }_{d}}\],\[{{\mu }_{p}}\]and\[{{\mu }_{f}}\]respectively, then
  A)
  \[{{\mu }_{d}}=0\] and \[{{\mu }_{p}}\ne 0\] done clear
  B)
  \[{{\mu }_{d}}\ne 0\] and \[{{\mu }_{p}}=0\] done clear
  C)
  \[{{\mu }_{p}}=0\] and \[{{\mu }_{f}}\ne 0\] done clear
  D)
  \[{{\mu }_{d}}\ne 0\] and \[{{\mu }_{f}}\ne 0\] done clear
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• question_answer78)
  The basic magnetization curve for a ferromagnetic material is shown in figure. Then, the value of relative permeability is highest for the point                  
  A)
  P done clear
  B)
  Q     done clear
  C)
  R    done clear
  D)
  S done clear
  View Solution play_arrow

• question_answer79)
  A domain in a ferromagnetic substance is in the form of a cube of side length\[1\mu m\]. If it contains \[8\times {{10}^{10}}\] atoms and each atomic dipole has a dipole moment of \[9\times {{10}^{-24}}\,A\,,{{m}^{2}}\], then the magnetization of the domain is
  A)
  \[7.2\times {{10}^{5}}\,A\,{{m}^{-1}}\] done clear
  B)
  \[7.2\times {{10}^{3}}\,A\,{{m}^{-1}}\] done clear
  C)
  \[7.2\times {{10}^{9}}\,A\,{{m}^{-1}}\] done clear
  D)
  \[7.2\times {{10}^{12}}\,A\,{{m}^{-1}}\] done clear
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• question_answer80)
  A Rowland ring of mean radius 15 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field B in the core for a magnetising current of l .2 amp?
  A)
  4.48 T   done clear
  B)
  2.48 T done clear
  C)
  5.48 T   done clear
  D)
  3.12T done clear
  View Solution play_arrow

• question_answer81)
  An example of a perfect diamagnet is a superconductor. This implies that when a superconductor is put in a magnetic field of intensity B, the magnetic field \[{{B}_{s}}\] inside the superconductor will be such that:
  A)
  \[{{B}_{s}}=-B\]          done clear
  B)
  \[{{B}_{s}}=0\] done clear
  C)
  \[{{B}_{s}}=B\]           done clear
  D)
  \[{{B}_{s}}<B\] but \[Bs\ne 0\] done clear
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• question_answer82)
  If the susceptibility of dia, para and ferromagnetic materials are\[{{\chi }_{d,\,}}\,{{\chi }_{p,}}\,{{\chi }_{f}}\] respectively, then
  A)
  \[{{\chi }_{d}}<{{\chi }_{p}}<{{\chi }_{f}}\]      done clear
  B)
  \[{{\chi }_{d}}<{{\chi }_{f}}<{{\chi }_{p}}\] done clear
  C)
  \[{{\chi }_{f}}<{{\chi }_{d}}<{{\chi }_{p}}\] done clear
  D)
         \[{{\chi }_{f}}<{{\chi }_{p}}<{{\chi }_{d}}\] done clear
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• question_answer83)
  A bar magnet has coercivity \[4\times {{10}^{5}}\,A{{m}^{-1}}\]. It is desired to demagnetise it by inserting it inside a solenoid 12 cm long and having 60 turns. The current that should be sent through the solenoid is
  A)
  2 A       done clear
  B)
  4 A   done clear
  C)
  6 A       done clear
  D)
  8 A done clear
  View Solution play_arrow

• question_answer84)
  The mass of a speciment of a ferromagnetic material is 0.6 kg. and its density is \[7.8\times {{10}^{3}}\,kg/{{m}^{3}}\]. If the area of hysteresis loop of alternating magnetising field of frequency 50Hz is 0.722 MKS units then the   hysteresis loss per second will be                           
  A)
  \[277.7\times {{10}^{-5}}\,joule\] done clear
  B)
  \[277.7\times {{10}^{-6}}\,joule\] done clear
  C)
  \[277.7\times {{10}^{-4}}\,joule\] done clear
  D)
  \[27.77\times {{10}^{-4}}\,joule\] done clear
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• question_answer85)
  The coercivity of a small magnet where the ferromagnet gets demagnetized is\[3\times {{10}^{3}}\,A{{m}^{-1}}\]. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetized when inside the solenoid, is:             
  A)
  30 mA  done clear
  B)
  60 mA done clear
  C)
  3 A   done clear
  D)
  6 A done clear
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