# Solved papers for JEE Main & Advanced Physics Magnetism JEE PYQ-Magnetism

### done JEE PYQ-Magnetism Total Questions - 39

• question_answer1) A thin rectangular magnet suspended freely has a period of oscillation equal to T. Now, it is broken into two equal halves (each having half of the original length) and one piece is made to oscillate freely in the same field. If its period of oscillation is T', the ratio T'/T is   [AIEEE 2003]

A)
$\frac{1}{2\sqrt{2}}$

B)
$\frac{1}{2}$

C)
2

D)
$\frac{1}{4}$

• question_answer2) A magnetic needle lying parallel to a magnetic field requires W unit of work to turn it through${{60}^{o}}$. The torque needed to maintain the needle in this position will be                     [AIEEE 2003]

A)
$\sqrt{3}$ W

B)
W

C)
$(\sqrt{3}/2)$W

D)
2 W

• question_answer3) The magnetic lines of force inside a bar magnet [AIEEE 2003]

A)
are from north-pole to south-pole of the magnet

B)
do not exist

C)
depend upon the area of cross-section of the bar magnet

D)
are from south-pole to north-pole of the magnet

• question_answer4) Curie temperature is the temperature above which                                      [AIEEE 2003]

A)
a ferromagnetic material becomes paramagnetic

B)
a paramagnetic material becomes  diamagnetic

C)
a ferromagnetic material becomes diamagnetic

D)
a paramagnetic material becomes ferromagnetic

• question_answer5) 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 [AIEEE 2004]

A)
$2s$

B)
$2/3\text{ }s$

C)
$2\sqrt{3}\text{ }s$

D)
$2/\sqrt{3}\text{ }s$

• question_answer6) A magnetic needle is kept in a non-uniform magnetic field. It experiences      [AIEEE 2005]

A)
a torque but not a force

B)
neither a force nor a torque

C)
a force and a torque

D)
a force but not a torque

• question_answer7) Needles ${{N}_{1}},{{N}_{2}}$ and ${{N}_{3}}$ are made of a ferromagnetic, a paramagnetic and a diamagnetic substance, respectively. A magnet when brought close to them will    [AIEEE 2006]

A)
Attract${{N}_{1}}$and${{N}_{2}}$strongly but repel${{N}_{3}}$

B)
Attract${{N}_{1}}$strongly, ${{N}_{2}}$weakly and repel${{N}_{3}}$ weakly

C)
Attract${{N}_{1}}$strongly, but repel${{N}_{2}}$and${{N}_{3}}$weakly

D)
attract all three of them

• question_answer8) Relative permittivity and permeability of a material are ${{\varepsilon }_{r}}$ and ${{\mu }_{r}}$, respectively. Which of the following values of these quantifies are allowed for a diamagnetic material? [AIEEE 2008]

A)
${{\varepsilon }_{r}}=0.5,\,{{\mu }_{r}}=0.5$

B)
${{\varepsilon }_{r}}=1.5,\,{{\mu }_{r}}=1.5$

C)
${{\varepsilon }_{r}}=0.5,\,{{\mu }_{r}}=1.5$

D)
${{\varepsilon }_{r}}=1.5,\,{{\mu }_{r}}=0.5$

• question_answer9) A bar magnet of length 6 cm has a magnetic moment of $4J\,{{T}^{-1}}.$Find the strength of magnetic field at a distance of 200 cm from the centre of the magnet along its equatorial line. [JEE ONLINE 07-05-2012]

A)
$4\times {{10}^{-8}}\text{tesla}$

B)
$3.5\times {{10}^{-8}}\text{tesla}$

C)
$5\times {{10}^{-8}}\text{tesla}$

D)
$3\times {{10}^{-8}}\text{tesla}$

• question_answer10) Two short bar magnets of length 1 cm each have magnetic moments 1.20$A{{m}^{2}}$and 1.00$A{{m}^{2}}$respectively. They are placed on a horizontal table parallel to each other with their N poles pointing towards the South. They have a common magnetic equator and are separated by a distance of 20.0 cm. The value of the resultant horizontal magnetic induction at the mid - point O of the line joining their centre is close to (Horizontal component of earth′s magnetic induction is$3.6\times {{10}^{-5}}Wb/{{m}^{2}}$)  [JEE MAIN 2013]

A)
$3.6\times {{10}^{-5}}Wb/{{m}^{2}}$

B)
$2.56\times {{10}^{-4}}Wb/{{m}^{2}}$

C)
$3.50\times {{10}^{-4}}Wb/{{m}^{2}}$

D)
$5.80\times {{10}^{-4}}Wb/{{m}^{2}}$

• question_answer11) The earths magnetic field lines resemble of a dipole at the centre of the earth. It the magnetic moment of this dipole is close to $8\times {{10}^{22}}$$\text{A}{{\text{m}}^{\text{2}}}$, the value of earths magnetic field near the equator is close to (radius of earth = $\text{6}\text{.4}\times \text{1}{{\text{0}}^{\text{6}}}\operatorname{m}$)        [JEE ONLINE 25-04-2013]

A)
0.6 Gauss

B)
1.2 Gauss

C)
1.8 Gauss

D)
032 Gauss

• question_answer12) The coercivity of a small magnet where the Ferro magnet 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:                       [JEE MAIN 2014]

A)
3 A

B)
6 A

C)
30 mA

D)
60 mA

• question_answer13)  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:           [JEE ONLINE 09-04-2014]

A)
1

B)
2

C)
3

D)
4

• question_answer14) The magnetic field of earth at the equator is approximately $4\times {{10}^{-5}}T.$The radius of earth is $6.4\times {{10}^{6}}m.$ Then the dipolemoment of the earth will be nearly of the order of:                           [JEE ONLINE 09-04-2014]

A)
${{10}^{23}}A{{m}^{2}}$

B)
${{10}^{20}}A{{m}^{2}}$

C)
${{10}^{16}}A{{m}^{2}}$

D)
${{10}^{10}}A{{m}^{2}}$

• question_answer15)  Three identical bars A, B and C are made of different magnetic materials. When kept in a uniform magnetic field, the field lines around them look as follows:             [JEE ONLINE 11-04-2014]

A)
$A\leftrightarrow D,B\leftrightarrow P,C\leftrightarrow F$

B)
$A\leftrightarrow F,B\leftrightarrow D,C\leftrightarrow P$

C)
$A\leftrightarrow P,B\leftrightarrow F,C\leftrightarrow D$

D)
$A\leftrightarrow F,B\leftrightarrow P,C\leftrightarrow D$

• question_answer16) 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: [JEE ONLINE 19-04-2014]

A)
${{B}_{s}}=-B$

B)
${{B}_{s}}=0$

C)
${{B}_{s}}=B$

D)
${{B}_{s}}<B$but$Bs\ne 0$

• question_answer17) A 25 cm long solenoid has radius 2 cm and 500 total number of turns. It carries a current of 15 A. If it is equivalent to a magnet of the same size and magnetization $\overset{\to }{\mathop{M}}\,$(magnetic moment/volume), then $|\overset{\to }{\mathop{M}}\,|$is:          [JEE ONLINE 10-04-2015]

A)
$30000\,A{{m}^{-1}}$

B)
$3\pi \,A{{m}^{-1}}$

C)
$30000\pi \,A{{m}^{-1}}$

D)
$300\,A{{m}^{-1}}$

• question_answer18)  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: [JEE MAIN 11-04-2015] (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)
9.7

B)
4.9

C)
19.4

D)
14.6

• question_answer19)  Hysteresis loops for two magnetic materials A and B are given below: [JEE MAIN - I 3-4-2016] These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use;

A)
B for electromagnets and transformers.

B)
A for electric generators and transformers.

C)
A for electromagnets and B for electric transformers.

D)
A for transformers and B for electric generators.

• question_answer20) A magnetic dipole is acted upon by two magnetic fields which are inclined to each other a tan angle of 75°. One of the fields has magnitude of 15mT. The dipole attains stable equilibrium at an angle 30° with this field. The magnitude of the other field (in mT) is close to:                              [JEE ONLINE 09-04-2016]

A)
11

B)
1060

C)
36

D)
1

• question_answer21) A fighter plane of length 20m, wing span (distance from tip of one wing to the tip of the other wing) of 15 m and height 5m is flying towards east over Delhi. Its speed is $240\,m{{s}^{-1}}$The earth's magnetic field over Delhi is $5\times {{10}^{-5}}$T with the declination angle $\sim {{0}^{o}}$ and dip of $\theta$ such that sin $\theta =\frac{2}{3}$.If the voltage developed is ${{V}_{B}}$ between the lower and upper side of the plane and ${{V}_{w}}$. between the tips the wings then ${{V}_{B}}$ and VW are closed to:                           [JEE ONLINE 10-04-2016]

A)
${{V}_{B}}=40mV,{{V}_{w}}=135mV$with left side of pilot at higher voltage.

B)
${{V}_{B}}=40mV,{{V}_{w}}=135mV$with right side of pilot at high voltage.

C)
${{V}_{B}}=45mV,{{V}_{w}}=120mV$with left side of pilot at higher voltage.

D)
${{V}_{B}}=45mV,{{V}_{w}}=120mV$with right side of pilot at higher voltage.

• question_answer22) A magnetic needle of magnetic moment $6.7\times {{10}^{-2}}\,A{{m}^{2}}$and moment of inertia $7.5\times {{10}^{-6}}\,kg\,{{m}^{2}}$is performing simple harmonic oscillations in a magnetic field of 0.01 T. Time taken for 10 complete oscillations is: [JEE Main 2017]

A)
6.98 s

B)
8.76 s

C)
6.65 s

D)
8.89 s

• question_answer23) A magentic dipole in a constant magnetic field has -                                  [JEE Online 08-04-2017]

A)
maximum potential energy when the torque is maximum

B)
zero potential energy when the torque is maximum

C)
zero potential energy when the torque is minimum

D)
minimum potential energy when the torque is maximum

• question_answer24)  The B-H curve for a Ferro magnet is shown in the figure. The Ferro magnet is placed inside a ling solenoid with 1000 turns/cm. The current that should be passed in the solenoid to demagnetise the Ferro magnet completely is: [JEE Online 15-04-2018]

A)
$2mA$

B)
$1mA$

C)
$40\mu A$

D)
$20\mu A$

• question_answer25) A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The coercivity of the bar magnet is:                                                     [JEE Main 09-Jan-2019 Morning]

A)
2600 A/m

B)
1200 A/m

C)
520 A/m

D)
285 A/m

• question_answer26)  In the given circuit the internal resistance of the 18 V cell is negligible. If ${{R}_{1}}\,\,=\,\,400\,\Omega$,  ${{R}_{3}}=100\text{ }\Omega$ and ${{R}_{4}}=500\Omega$and the reading of an ideal voltmeter across ${{R}_{4}}$ is 5 V, then the value of ${{R}_{2}}$ will be: [JEE Main 09-Jan-2019 Evening]

A)
$550\,\,\Omega$

B)
$450\,\,\Omega$

C)
$230\,\,\Omega$

D)
$300\,\,\Omega$

• question_answer27) A magnet of total magnetic moment ${{10}^{-}}^{2}\widehat{i}\,A-{{m}^{2}}$ is placed in a time varying magnetic field, $B\widehat{i}\left( cos\text{ }\omega t \right)$ where $B=1$ Tesla and$\omega =0.125\text{ }rad/s$. The work done for reversing the direction of the magnetic moment at $t=1$ second, is- [JEE Main 10-Jan-2019 Morning]

A)
0.014 J

B)
0.028 J

C)
0.01 J

D)
0.007 J

• question_answer28) A solid metal cube of edge length 2 cm is moving in a positive y-direction at a constant speed of 6 m/s. There it, a uniform magnetic field of 0.1 T in the positive z- direction. The potential difference between the two faces of the cube perpendicular to the x-axis, is - [JEE Main 10-Jan-2019 Morning]

A)
2 mV

B)
12 mV

C)
6 mV

D)
1 mV

• question_answer29) At some location on earth the horizontal component of earths magnetic field$18\times {{10}^{-}}^{6}T$. At this location, magnetic needle of length 0.12 m and pole strength 1.8 Am is suspended from its mid-point using a thread, it makes $45{}^\circ$ angle with horizontal in equilibrium. To keep this needle horizontal, the vertical force that should be applied at one of its ends is-         [JEE Main 10-Jan-2019 Evening]

A)
$3.6\times {{10}^{-5}}\,N$

B)
$1.8\times {{10}^{-5}}\text{ }N$

C)
$1.3\times {{10}^{-5}}\,N$

D)
$6.5\times {{10}^{-5}}\,N$

• question_answer30) A hope and a solid cylinder of same mass and radius are made of a permanent magnetic material with their magnetic moment parallel to their respective axes. But the magnetic moment of hoop is twice of solid cylinder. They are placed in a uniform magnetic field in such a manner angle with the field. If the oscillation periods of hoop and cylinder are ${{T}_{h}}\text{ }and\text{ }{{T}_{c}}$ respectively, then- [JEE Main 10-Jan-2019 Evening]

A)
${{T}_{h}}=1.5\text{ }{{T}_{c}}$

B)
${{T}_{h}}={{T}_{c}}$

C)
${{T}_{h}}=2{{T}_{c}}$

D)
${{T}_{h}}=0.5{{T}_{c}}$

• question_answer31) In an experiment, electrons are accelerated, from rest, by applying a voltage of 500 V. Calculate the radius of the path if a magnetic field 100 mT is then applied. [Charge of the electron $=1.6\times {{10}^{-16}}C,$ Mass of the electron $=9.1\times {{10}^{-31}}kg$]                                                        [JEE Main 11-Jan-2019 Morning]

A)
$7.5m$

B)
$7.5\times {{10}^{-2}}m$

C)
$7.5\times {{10}^{-4}}m$

D)
$7.5\times {{10}^{-3}}m$

• question_answer32) A paramagnetic substance in the form of a cube with sides 1 cm has a magnetic dipole moment of $20\times {{10}^{-6}}J/T$ when a magnetic intensity of $60\times {{10}^{3}}A/m$is applied. Its magnetic susceptibility is- [JEE Main 11-Jan-2019 Evening]

A)
$3.3\times {{10}^{-2}}$

B)
$4.3\times {{10}^{-2}}$

C)
$3.3\times {{10}^{-4}}$

D)
$2.3\times {{10}^{-2}}$

• question_answer33)  As shown in, the figure, two infinitely long, identical wires are bent by $90{}^\circ$ and placed in such a way that the segments LP and QM are along the x-axis, while segments PS and QN are parallel to the y-axis. If OP=OQ=4cm, and the magnitude of the magnetic field at C) is${{10}^{-4}}T,$ and the two wires carry equal currents (see figure), the magnitude of the current in each wire and the direction of the magnetic field at O will be- [JEE Main 12-Jan-2019 Morning] $({{\mu }_{0}}=4\pi \times {{10}^{-7}}N{{A}^{-2}})$

A)
20 A, perpendicular into the page

B)
40 A, perpendicular into the page

C)
20 A, perpendicular out of the page

D)
40 A, perpendicular out of the page.

• question_answer34) A paramagnetic material has${{10}^{28}}\,\,atoms/{{m}^{3}}$. Its magnetic susceptibility at temperature 350 K is $2.8\times {{10}^{-4}}.$ Its susceptibility at 300 K is-                  [JEE Main 12-Jan-2019 Evening]

A)
$3.267\times {{10}^{-4}}$

B)
$3.672\times {{10}^{-4}}$

C)
$2.672\times {{10}^{-4}}$

D)
$3.726\times {{10}^{-4}}$

• question_answer35)  Two magnetic dipoles X and Y are placed at a separation d, with their axes perpendicular to each other. The dipole moment of Y is twice that of X. A particle of charge q is passing, through their midpoint P, at angle $\theta ={{45}^{o}}$with the horizontal line, as shown in figure. What would be the magnitude of force on the particle at that instant? (d is much larger than the dimensions of the dipole)  [JEE Main 8-4-2019 Afternoon]

A)
$\sqrt{2}\left( \frac{{{\mu }_{0}}}{4\pi } \right)\frac{M}{{{(d/2)}^{3}}}\times q\text{v}$

B)
$\left( \frac{{{\mu }_{0}}}{4\pi } \right)\frac{2M}{{{(d/2)}^{3}}}\times q\text{v}$

C)
$\left( \frac{{{\mu }_{0}}}{4\pi } \right)\frac{M}{{{(d/2)}^{3}}}\times q\text{v}$

D)
0

• question_answer36) A moving coil galvanometer has a coil with 175 turns and area $1c{{m}^{2}}.$It uses a torsion band of torsion constant ${{10}^{-6}}$ N-m/rad. The coil is placed in a maganetic field B parallel to its plane. The coil deflects by$1{}^\circ$for a current of 1 mA. The value of B (in Tesla) is approximately: [JEE Main 9-4-2019 Afternoon]

A)
${{10}^{-3}}$

B)
${{10}^{-1}}$

C)
${{10}^{-4}}$

D)
${{10}^{-2}}$

In a meter bridge experiment, the circuit diagram and the corresponding observation table are shown in figure
 SI. No. $R(\Omega )$ $l(cm)$ 1. 1000 60 2. 100 13 3. 10 1.5 4. 1 1.0
Which of the readings is inconsistent? [JEE Main 10-4-2019 Morning]

A)
4

B)
1

C)
2

D)
3

• question_answer38) A magnetic compass needle oscillates 30 times per minute at a place where the dip is $45{}^\text{o},$and 40 times per minute where the dip is $30{}^\text{o}$. If ${{B}_{1}}$and ${{B}_{2}}$are respectively the total magnetic field due to the earth at the two places, then the ratio ${{B}_{1}}/{{B}_{2}}$is best given by: [JEE Main Held on 12-4-2019 Morning]

A)
2.2

B)
1.8

C)
0.7

D)
3.6

• question_answer39)  The figure gives experimentally measured B vs. H variation in a ferromagnetic material. The retentivity, co-ercivity and saturation, respectively, of the material are [JEE MAIN Held on 07-01-2020 Evening]

A)
1.0 T, 50 A/m and 1.5 T

B)
1.5 T, 50 A/m and 1.0 T

C)
1.5 T, 50 A/m and 1.0 T

D)
150 A/m, 1.0 T and 1.5 T