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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
A magnetic of magnetic moment placed along the X-axis in an magnet field .Find the torque acting on the magnetic field |
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Answer» `therefore " " "Torque", tau=MxxB` where, M is magnetic moment and B is a magnetic field Given, `M=50hatiA-m^(2),B=0.5hati+3hatiT` `therefore " " tau=50hati(0.5hati+3hatj)` `"Using" hatixxhatj=hatk, "we have" ` `" " tau=150hatk N-m` |
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| 52. |
A closely wound solenoid of 800 turns and area of cross section `2*5xx10^-4m^2` carries a current of `3*0A`. Explain the sense in which the solenoid acts like a bar magnet. What is its associated magnetic moment? |
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Answer» It is given that number of turns, N=800N Area of cross-section, A=`2.5xx10^(4)m^(2)` Now, magnetic moment of the solenoid is `" " M=NIA=800xx3.0xx2.5xx10^(-4)` `" " =0.60JT^(-1)` Which acts along the axis of the solenoid in the direction releated to the sence of flow of current according to right handed screw rule. |
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| 53. |
If a magnetic material is having magnetic susceptibility `(chi)=-1` thent he relative magnetic permeability `(mu_(r))` and type of mangnetic material isA. 0, diamagneticB. 2,ferromagneticC. 1,paramagneticD. `-1,"diamagnetic"` |
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Answer» Correct Answer - A `Here, chi=-1` `then, mu_(r)=1+chi Rightarrow mu_(r)=1+(-1)=1-1=0` Since magnetic susceptibility of given material is less than one. Hence the give magnetic material isa diamagnetic material |
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| 54. |
For ferromagnetic material, the relative permeability (mu_(r)), versus magnetic intensity (H) has the following shapeA. B. C. D. |
| Answer» Correct Answer - D | |
| 55. |
If a ferromagnetic material is inserted in a current carring solenoid, the magnetic field of solenoidA. Largely increasesB. Slightly increasesC. Largely decreasesD. Slightly decreases |
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Answer» Correct Answer - A Theory based |
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| 56. |
A straight wire carring current I is turned into a circular loop. If the magnitude of magnetic moment associated with it in M.K.S. unit is M, the length of wire will beA. `4piiM`B. `sqrt((4piM)/i)`C. `sqrt((4pii)/M)`D. `(Mpi)/(4i)` |
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Answer» Correct Answer - B Megnetic moment of circular loop carrying current `M=IA=I(piR^(2))=Ipi(L/(2pi))^(2)=(IL^(2))/(4pi) implies L=sqrt((4piM)/I)` |
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| 57. |
Essential difference between electrostatic shielding by a conducting shell and magnetostatic shielding is due toA. electrostatic field lines can end on charges and conductors have free chargesB. lines of B can also end but conductors cannot end themC. lines of B cannot end on any material and perfect shieldin g is not possibleD. shells of high permeability can be used to divert lines of B from the interior region. |
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Answer» Electrostatic shielding is the phenomenon to block the effects of an electric field. The conducting shell can block the effects of an external field on its interanl content or the effect of an internal held on the outside environmen t. Magnetostatic shielding is done by using an enclosure made of a high permeability magnetic material to prevent a static magnetic field outside the enclosure from reaching objects inside it or to confine a magnetic field within the enclosure. |
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| 58. |
Classify the following materials with regard to magnetism : Maganese, Cobalt, Nickel, Bismuth, Oxygen, Copper. |
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Answer» Manganese - Para magnetic Cobalt - Ferromagnetic Nickel - Ferromagnetic Bismuth - Diamagnetic Oxygen - Paramagnetic Copper - Diamagnetic |
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| 59. |
A proton has spin and magnetic moment just like an electron. Why then its effect is neglected in magnetism of materials? |
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Answer» The comparison b etween the spinning of a proton and an electron can be done by comparing their magnetic dipole moment which can b e given by `M=(eh)/(4 pim)"or" M=(1)/(m) (because (eh)/(4pi)="constant")` `therefore (M_(P))/(M_( e))=(m_(b))/(m_(p))` `=(M_(e))/(1837M_(e)) (because M_(p)=1837 m_(e))` `rArr (M_(P))/(M_(e))=(1)/(1837)ltlt1` `rArr (M_(P)ltltM_(e)` ltbr. Thus, effect of magnetic moment of proton is neglected as compared to that of electron. |
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| 60. |
Calculate the magnetic induction at a point 1 away from a proton, measured along its axis of spin. The magnetic moment of the proton is `1.4xx10^(-26)A-m^(2)` |
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Answer» Ont the axis of a magnetic dipole, magnetic induction is given by `" " B=(mu_(0))/(4pi), (2M)/(r^(2))` Substituting the values, we get `" " B=(10^(-7)-(2)(1.4xx10^(-26)))/((10^(-10))^(3))=2.8xx10^(-3) T=2.8mT` |
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| 61. |
The magnet induction at a point 1 Ã… away from a proton measured along its axis of spin is (magnetic moment of the proton is `1.4xx10^(-26)"A m"^(2)`)A. 0.28 mTB. 28 mTC. 0.028 mTD. 2.8 mT |
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Answer» Correct Answer - D On the axis of a magnetic dipoles, magnetic induction is `B=(mu_(0))/(4pi)xx(2m)/(r^(3))` Here, `r=1 Ã…= 10^(-10)" m", m= 1.4xx10^(-26)"A m"^(-2)` and `(mu)/(4pi)=10^(-7)"N A"^(-2)` `therefore" "B=(10^(-7)xx2xx1.4xx10^(-26))/((10^(-10))^(3))=(10^(-7)xx2.8xx10^(-26))/(10^(-30))` `" "=2.8xx10^(-3)` T = 2.8 mT |
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| 62. |
Assertion: Magnetic moment of an atoms is due to both, the orbital motion and spin motion of every electron. Reason: A charged partical produces a magnetic field.A. If both assertion and reason are true and reason is the correct explanation of assertion.B. If both assertion and reason are true but reason is not the correct explanation of assertion.C. If assertion is true but reason is false.D. If assertion and reason both are false. |
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Answer» Correct Answer - C In an atom, electrons revolve around the nucleus and as such the circular orbit of electrons may be considered as the small current loops. In addition to orbital motion, an electron has got spin motion also. So the total magnetic moment of electron is the vector sum of its magnetic moment due to orbital and spin motion. Charge particles at rest do not produce electric field. |
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| 63. |
The magnetic moment vectors `vecmu_s` and `vecmu_l` associated with the intrinsic spin angular momentum `vecS` and orbital angular momentum `vecl` respectively, of an electron are predicted by quantum theory (and verified experimentally to a high accuracy to be given by `vecmu_s=-(e/m)vecS` and `vecmu_l=-((e)/(2m))vecl` Which of these relations is in accordance with the result expected classically? Outline the derivation of the classical result. |
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Answer» Out of the two relations given only one is in accordance with classical physics. This is `vec(mu)_(1) = -((e)/(2m))vec(l)` It follows from the definitions of `mu_(1)` and l. `mu = iA = ((-e)/(T)) pi r^(2)`. `l = m v r = m((2pir)/(T))r` Where r is the radius of the circular orbi which the electron of mass m and charge (-e) completes in time T. Divide (i) by (ii) `(mu_(1))/(l) = (-e)/(T) pi r^(2) xx (T)/(m^(2) pi r^(2)) = (-e)/(2m)` `vec(mu)_(1) = ((-e)/(2m))vec(l)` Clearly `vec(mu)_(1)` and `vec(l)` will be antiparallel (both being normal to the plane of the orbit) In contrast `(mu_(s))/(s) = (e)/(m)`. It is obtained on the basis of quantum mechanics. |
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| 64. |
Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole moment (m). Which configuration has highest value of magnetic dipole moment?A. B. C. D. |
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Answer» Correct Answer - C `(a) M_(1)=msqrt2 ` `(b) underset(m)overset(m)(hArr) Rightarrow M_(2)=0` `(c) M_(3)=msqrt((1+cos 30^(@))2)` `" " msqrt((1+(sqrt3)/(2)))2=msqrt(2+sqrt3)` `(d) " " M_(4)=2m cos30^(@)=msqrt3` |
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| 65. |
The permeablitiy of paramgentic substance isA. slinght more than vacuumB. slight less than vacuumC. much more than vaccumD. None of the above |
| Answer» Correct Answer - A | |
| 66. |
The magnetic susceptibility of a paramagnetic material at `-73^(@)C "is" 0.0075`, its value at `-173^(@)C` will beA. 0.045B. 0.03C. 0.015D. 0.0075 |
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Answer» Correct Answer - C `"Here", chi_(m_(1))=0.075` `T_(1)=-73^(@)C=(-73+273)K=200K` `T_(2)=-173^(@)C=(-173+273)K=100K, chi_(m_(2))=?` As for paramagnetic material magnetic susceptibility `chi_(m)alpha(1)/(T) Rightarrow (chi_(m_(2)))/(chi_(m_(1)))=(T_(1))/(T_(2))=(200)/(100)=2` `therefore chi_(m_(2))=2chi_(m_(1))=2xx0.075=0.015` |
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| 67. |
Hysteresisis exhibited by a ……….. . Substance.A. parmagneticB. ferromagneticC. diamagenticD. All of these |
| Answer» Correct Answer - B | |
| 68. |
A susceptibility of a certain magnetic material is 400. What is the class of the magnetic material?A. DiamagneticB. ParamagneticC. FerromagneticD. Ferroelectric |
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Answer» Correct Answer - C The class of the magnetic material is ferromagnetic. |
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| 69. |
A compose needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. ItA. will stay in east-west direction onlyB. will become rigid showing no movementC. will stay in any positionD. will stay in north-south direction only |
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Answer» Correct Answer - B It will stay in any position at geomagnetic north and south poles. |
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| 70. |
A solenoid has core of a material with relative permeability 500 and its windings carry a current of 1 A. The number of turns of the solenoid is 500per meter. The magnetization of the material is nearlyA. `2.25xx10^(3)Am^(-1)`B. `2.25xx10^(5)Am^(-1)`C. `2.0xx10^(3)Am^(-1)`D. `2.0xx10^(5)Am^(-1)` |
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Answer» Correct Answer - B Here, n=5000turns/m `I=1A, mu_(r)=500` `"Magnetic intensity", H=nI=500m^(-1)xx1A=500Am^(-1)` `As, mu_(r)=1+chi` Where, `chi` is the magnetic susceptibility of the material `or chi=(mu_(r)-1)` Magnesium, `M=chiH` `=(mu_(r)-1)H=(500-1)xx500Am^(-1)` `=499xx500Am^(-1)=2.495xx10^(5)Am^(-1)` `approx 2.5xx10^(5)Am^(-1)` |
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| 71. |
Above the Curie temperature, the susceptility of a ferromagentic substance varies |
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Answer» Correct Answer - B Above the Curie temperature, ferrromagnetic susbstance become paramagnetic in nature. |
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| 72. |
If a magnetic substance is kept in a magnetic field, then which of the following is thrown out?A. ParamagneticB. FerromagneticC. DiamagneticD. Antiferromagnetic |
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Answer» Correct Answer - C Diamagnetic substances are repelled by magnetic field. |
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| 73. |
Define magnetic susceptibility of a material. Name two elements one having positive susceptibility and other having negative susceptibility. |
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Answer» (1) Susceptibility : When a material is placed in a magnetic field, the ratio of the intensity of magnetization acquired by it to the intensity of the applied magnetic field is called its susceptibility. Suspectibility `chi = ("Intensity of magnetisation , I")/("Applied magnetic field, H")` (2) The susceptibility of a material represents its ability to get magnetism. (3) Susceptibility is a dimension less quantity. (4) Relation between `mu_(r)` and `chi` : (a) Suppose that material is placed in a magnetic field of intensity H. Ley I be the intensity of magnetisation acquired by it. (b) Then the magnetic induction with in the material is `B = mu_(0) H + mu_(0)I rArr (B)/(H) = mu_(0)[1+(I)/(H)]` `rArr mu = mu_(0)[1+ chi] rArr (mu)/(mu_(0)) = 1+chi` `:. mu_(r) = 1+ chi [because mu_(r) = (mu)/(mu_(0))]` (5) Negative susceptibility `(chi)` of diamagnetic elements are Bismuth `(-1.66 xx 10^(-5))` and copper `(-9.8 xx 10^(-6))`. (6) Positive susceptibility of Ferromagnetic elements are Aluminium `(2.3 xx 10^(-5))` and oxygen at STP `(2.1 xx 10^(-6))`. (7) Large and positive susceptibility of ferromagnetic elements are Cobalt and Nickel. |
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| 74. |
The magnetic susceptibility is negative forA. diamagnetic material onlyB. paramagnetic material onlyC. ferromagnetic material onlyD. paramagnetic and ferromagnetic materials |
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Answer» Correct Answer - A Mgnetic susceptibility `= chi` it is negative for diamagnetic materials only |
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| 75. |
Out of dia, para and ferromagnetism, the universal property of all substances isA. diamagnetismB. ferro magnesiumC. paramagneticD. all of these |
| Answer» Correct Answer - A | |
| 76. |
A frog can be levitated in a strong magnetic field below it . This is possible because the body of the frog behaves asA. ParamagneticB. DiamagneticC. FerromagneticD. Anti ferromagnetic |
| Answer» Correct Answer - B | |
| 77. |
Assertion: Substances which at room temperature retain their ferromagnetic property for a long period of time are called permanent magnets. Reason: permanent magnet can be made by placing a ferramagnetic rod in a solenoid and passing current through it.A. If both assertion and reason are true and reason is the correct explanation of assertion.B. If both assertion and reason are true and reason is not the correct explanation of assertion.C. If assertion is ture but reason is false.D. If both assertion and reason are false. |
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Answer» Correct Answer - B To make a permanent magnet, place a ferromagnetic rod in a solenoid and pass a current through it. The magnetic field of the solenoid magnetises the rod. |
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| 78. |
The only property possessed by ferromagnetic substance isA. hysteresisB. susceptiilityC. directional propertyD. attracting magnetic substances |
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Answer» Correct Answer - A Some peculiar properties of ferromagnetic materials ar commently displayed by curve of B against H which is called B-H curve or hysteresis is B loop. Dia and para do not show these properties |
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| 79. |
When a magnetic substance is heated, then itA. Becomes a strong magnetB. losses its magnetismC. Does not effect the magnetismD. Either (a) or (c ) |
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Answer» Correct Answer - B Theory based |
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| 80. |
Which of following property shows the property of ferromagnetic substances?A. The ferromagnetic property depends, on temperature.B. The ferromagnetic property does not depend on temperature.C. At high enough temperature ferromagnet becomes a diamagnet.D. At low temperature ferromagnet becomes a paramagnet. |
| Answer» Correct Answer - A | |
| 81. |
A solenoid having 2000 turns/m has a core of a material with relative permeability 220. The area of core is `4cm^(2)` and carries a current of 5A. Calculate (a) Magnetic intensity (b) Magneic field (c ) Magnetisation (I) of the core Also calculate the pole strength developed. |
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Answer» Given `n=2000 turns,I=5A, mu_(r)=220,A=4cm^(2)` (a) Magnetic intensity, `H=nI=2000xx5=1000A//m` (b) Magnetic field, `B=muH=mu_(0)mu_(r)h` `" " 4pixx10^(-7)xx220xx10000=88pixx10^(-2)T` (C ) As we know , `B=B_(0)(H+I)` `" "88pixx10^(-2)=10^(4)+I` `Rightarrow 2.20xx10^(6)=10^(4)+I` `" " I=(2.20xx10^(6)-10^(4))=2.19xx10^(6)A//m` (d) Pole strength, m=`(2.19xx10^(6))(4xx10^(-4))=876A//m` |
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| 82. |
STATEMENT-1 : Above Curie temperature substance is converted to paramagnetic substance. and STATEMENT-2 : As the Curie temperature is reached , the energy associated with thermal motion becomes large enough compared to the interaction energy responsible for the spontaneous alignment of magnetic moments .A. Statement-1 is True , Statement-2 is True , Statement-2 is a correct explanation for Statement-1B. Statement-1 is True , Statement-2 is True , Statement-2 is NOT a correct explanation for Statement- 1C. Statement-1 is True , Statement-2 is FalseD. Statement-1 is False , Statement-2 is True |
| Answer» Correct Answer - A | |
| 83. |
A solenoid , of insulated wire, is wound on a core with relative permeability 400. If the number of turns per metre is 1000 and the solenoid carries a current of 2A, calculate H, B and the magnetisation M. |
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Answer» Given , `mu_(r) = 400, I = 2A, n = 1000` `H = nI = 1000 xx 2 = 2 xx 10^(3)A//m` `B = mu_(r).mu_(0)H = 400 xx 4pi xx 10^(-7) xx 2 xx 10^(3) = 1.0 T` Magnetisation `M = (mu_(r) -1)H = (400 - 1)H = 399 xx 2 xx 10^(3)` `:. M ~= 8 xx 10^(5) A//m` |
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| 84. |
Assertion : The product of magnetic susceptibility and absolute temperature for a paramagnetic substance is constant. Reason: Susceptibility is positive but very small for paramagnetic substance.A. If both assertion and reason are true and reason is the correct explanation of assertion.B. If both assertion and reason are true and reason is not the correct explanation of assertion.C. If assertion is ture but reason is false.D. If both assertion and reason are false. |
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Answer» Correct Answer - B The susceptibility of a paramagnetic substance is inversely proportional to absolute temperature `chi alpha (1)/(T)` Hence, `chi T="constant"` Also for paramagnetic substances the susceptibility is positive and very small.. |
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| 85. |
The magnetic susceptibility is negative forA. diamagnetism materialsB. Paramagnetic materialsC. Ferromagnetic materialsD. all of these |
| Answer» Correct Answer - A | |
| 86. |
A diamagnetic substance when placed gently in a magnetic field movesA. From weaker to the stronger parts of the fieldB. From stronger to the weaker parts of the fieldC. Perpendicular to the fieldD. Does not move |
| Answer» Correct Answer - B | |
| 87. |
Diamagnetic subtance areA. Feebly attracted by magnetsB. Strongly attracted by magnetsC. Feebly repelled by magnetsD. Strongly repelled by magnets |
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Answer» Correct Answer - C Theory based |
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| 88. |
The area of hysteresis loop of a material is equinalent to 250 joule. When 10 kg material is magnetised by an alternating field of 50 Hz then energy lost in one hour will be if the density of material is `7.5 gm//cm^(2)`A. `6xx10^(4)J`B. `6xx10^(4)erg`C. `3xx10^(2)J`D. `3xx10^(2)erg` |
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Answer» Correct Answer - A `E=nAVt=nAm/dt=(50xx250xx10xx3600)/(7.5xx10^(3))=6xx10^(4)` |
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| 89. |
Identify the paramagnetic substanceA. IronB. AluminiumC. NickelD. Hudrogen |
| Answer» Correct Answer - B | |
| 90. |
A solenoid having 5000 turns/m carries a current of 2A. An aluminium ring at temperature 300K inside the solenoid provides the core, (a) If the magnetisation I is `2xx10^(-2)A/m`. Find the susceptibility of aluminium at 300K (b) If temperature of the aluminium ring is 320K, what will be the magnetisation ? |
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Answer» `H=I=5000xx2=10^(4)A//m` `" " I=chiH` `" " chi=(I)/(H)=(2xx10^(2))/(10^(4))=2xx10^(-6)` (b) According to Curie law `" " chi=(C)/(T) Rightarrow (chi_(2))/(chi_(1))=(T_(2))/(T_(1))` `" " chi_(2)=(T_(2))/(T_(1))chi_(1)=(320)/(300)xx2xx10^(-6)=2.13xx10^(-6)` Manetisation at 320K `I=chi_(2)H=2.13xx10^(-6)xx10^(4)=2.13xx10^(-2)A//m` |
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| 91. |
Which of the following is not correct about the magnetic field lines?A. The magnetic field lines of a magnet form continuous closed loopsB. The tangent to the field line at a given point represents the direction of the net magnetic field B at that point.C. The larger the number of field lines crossing per unit area, the stronger is the magnitude of the magnetic field B.D. The magnetic field lines may intersect to each other in certain conditions. |
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Answer» Correct Answer - D The magnetic field lines do not intersect. |
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| 92. |
The magnetic moment of a diamagnetic substance isA. ZeroB. 1C. Less than 1D. Greater than 1 |
| Answer» Correct Answer - A | |
| 93. |
Substance in which the magnetic moment of a single atom is not zero, is know asA. DiamagnetismB. FerromagnetismC. ParamagnetismD. Ferrimagnetism |
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Answer» Correct Answer - C The property of paramagnetism is found in these substances whose atoms have an excess of electrons spinning in the same direction. Hence, atoms of paramagnetic substances have a net-zero magnetic moment of their own. |
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| 94. |
The magnetic moment produced in a substance of `1 gm is 6xx10^(-7) "ampere","metre"^(2)`. If its density is `5 gm//cm^(3)`, then the intensity of magnetisation in `A//m` will beA. `8.3xx10^(6)`B. `3.0`C. `1.2xx10^(-7)`D. `3xx10^(-6)` |
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Answer» Correct Answer - B `I=m/V=M/(mass//density)`, given `mass=1 gm=10^(-3) kg`, and density `=5 gm//cm^(3)=(5xx10^(-3)kg)/((10^(-2))m^(3))=5xx10^(3) kg//m^(3)` Hence `I=(6xx10^(-7)xx5xx10^(3))/10^(-3)=3` |
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| 95. |
Which of the following is true?A. Diamagnetism is temperature dependentB. Paramagnetism is temperature dependntC. Paramagnetism is magnetic independentD. None of these |
| Answer» Correct Answer - B | |
| 96. |
Magnetic moment for a solenoid and corresponding bar magnet isA. equal for bothB. more for solenoidC. more for bar magnetD. none of these |
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Answer» Correct Answer - A Since a bar magnet and a corresponding solenoid produce similar magnetic fields. Hence the magnetic moment of a bar magnet is equal to the magnetic moment of an equivalent solenoid that produces the same magnetic field. |
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| 97. |
Magnetic permeability is maximum forA. diamagnetic substanceB. paramagnetic substanceC. inversion temperatureD. all of these |
| Answer» Correct Answer - C | |
| 98. |
Substance in which the magnetic moment of a single atom is not zero, is know asA. diamagnetismB. ferromagnitismC. Paramagnetism is magnetic independentD. ferrimagneitsm |
| Answer» Correct Answer - C | |
| 99. |
Magnetic permeability is maximum forA. ferromagnetic substancesB. diamagnetic substancesC. paramagnetic substancesD. all of these |
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Answer» Correct Answer - A Magnetic permeability is maximm for ferromagnetic substances. |
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| 100. |
A domain in ferromagnetic iron in the form of cube shaving `5 xx 10^(10)` atoms. If the side length of this domain is `1.5mu` and each atom has a dipole moment of `8 xx 10^(-24)Am^(2)`, then magnetisation of domain isA. `11.8xx10^(5)Am^(-1)`B. `1.18xx10^(5)Am^(-1)`C. `11.8xx10^(4)Am^(-1)`D. `1.18xx10^(5)Am^(-1)` |
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Answer» Correct Answer - D The volume of the cubic domain is `V=(1.5xx10^(6)m)^(3)=3.38xx10^(-18)m^(3)=3.38xx10^(-12)cm^(3)` Number of atoms in doamain (N)=`5xx10^(10)"atoms"` Since each iron atoms has a dipole moment (m) `=8xx10^(-24)Am^(2)` `m_("max")`=total number of dipole moment for all atoms `=Nxxm` `=5xx10^(10)xx8xx10^(-24)` `=40xx10^(-14)=4xx10^(-13)Am^(2)` Now the consequent magnetisation `M_("max")=(m_("max"))/("Domain volume")=(4xx10^(-13)Am^(-2))/(3.38xx10^(-18)m^(3))` `=1.18xx10^(5)Am^(-1)` |
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