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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
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question_answer2)
A curve between magnetic moment and temperature of magnet is
A)
B)
C)
D)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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)
B)
C)
D)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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question_answer68)
The graph between\[\chi \]and 1/T for paramagnetic material will be represented by
A)
B)
C)
D)
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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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