Assertion: Diamagnetic materials can exhibit magnetism.Reaso

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 Multiple Choice QuestionsMultiple Choice Questions

71.

Which of the following is true regarding diamagnetic substaces symbols ( symbols have their usual meaning)

  • μ > 1, χm > 1

  • μ > 1, χm < 1

  • μr < 1, χm < 1

  • μ >1, χm < 1


72.

Assertion: The magnetic poles of earth do not coincide with the geographic poles. 

Reason:  The discrepancy between the orientation of a compass and true north-south direction is known as magnetic declination.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


73.

A  current  I1  carrying  wire  AB  is  placed  near  another   long  wire  CD  carrying  current I2. If  wire  AB  is  free  to  move,  it  will  have

  • rotational motion only

  • translational motion only

  • rotational as well as translational motion

  • neither rotational nor translational motion


74.

Assertion: Magnetic susceptibillity is a pure number. 

Reason: The value of magnetic susceptibility for vacuum is one.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false.


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75.

Lumen is the unit of

  • Luminous flux

  • luminosity

  • illumination

  • quantity of light


76.

Assertion: We cannot think of magnetic field configuration with three poles.

Reason: A bar magnet does exert a torque on itself to its own field.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


77.

Assertion:  The energy of charged particle moving in a uniform magnetic field does not change. 

Reason: Work done by magnetic field on the charge is zero

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion

  • If assertion is true but reason is false

  • If both assertion and reason are false


78.

The magnetic susceptibility of an ideal diamagnetic substance is

  • -1

  • 0

  • +1


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79.

The magnetic moment has dimensions of

  • [ LA ]

  • [ L2A ]

  • [ L T-1 A ]

  • [ L2 T-1 A ]


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80.

Assertion: Diamagnetic materials can exhibit magnetism.

Reason: Diamagnetic materials have permanent magnetic dipole moment.

  • If both assertion and reason are true and reason is the correct explanation of the assertion

  • If both assertion and reason are true but reason is not the correct explanation of the assertion

  • If assertion is true, but reason is false

  • Both assertion and reason are false statements.


D.

Both assertion and reason are false statements.

Some materials when placed in an external magnetic field, acquire a very low magnetism in a direction opposite to the field. These materials when brought near the end of a strong magnet, they get repelled. These materials are diamagnetic and this property of materials is  called diamagnetism. This property is generally found in materials in  which there are even number of electrons in their atoms ( or molecules ) and pairs are formed with two electrons. In each pair, the spin of one  electron is in direction opposite to the spin of other electron. Hence, the electrons of each pair completely cancel the magnetic moment of each other. Thus, the net magnetic moment of each atom of such material is zero. Hence, option (c) is true.


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