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NDA - Magnetism & Matter Test 1307
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NDA - Magnetism & Matter Test 1307
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  • Question 1/5
    1 / -0.33
    After heating a permanent Magnet it results in the loss of magnetic behaviour. It occurs due to
    Solutions

    Heating a permanent magnet causes vibration of magnetic dipoles, so their alignment in one particular direction is lesser so loss of magnetic behaviour.

    Due to Excessive heat atoms move more rapidly, and started disturbing the magnetic domains. As the atoms are speed up, the percentage of magnetic domains spinning in the same direction is decreases. This lack of cohesion weakens the magnetic force and eventually demagnetizes it entirely.

    In contrast, when a magnet is exposed to extreme cold, the atoms slow down so the magnetic domains are aligned and in turn it becomes, strengthened.

  • Question 2/5
    1 / -0.33
    Which of the following is SI UNIT of Magnetic permeability is?
    Solutions

    Magnetic permeability has SI unit Henry per meter that can also be represented as newtons per ampere square. Hence, option D is correct

  • Question 3/5
    1 / -0.33
    How are the magnetic susceptibility(χm) and relative magnetic permeability(μr) related for a magnetic material?
    Solutions

    Relative magnetic permeability is defined as the ratio of permeability of medium to the permeability of free space.

    Magnetic susceptibility is defined as the ratio of the intensity of magnetization M to the magnetizing field intensity H.

    For a linear magnetic material subjected to the action of a magnetizing field intensity H and develops magnetization M and induction B, we can write

    Where μ0 is the permeability of free space.

    We know that

    Comparing

    As  , so

    Hence D is the correct option.

  • Question 4/5
    1 / -0.33
    When a diamagnetic material placed in a magnetic field it moves:
    Solutions

    When diamagnetic material is placed in an external magnetic field, the spin motion of which produce the magnetic moments in the direction of external field slow down while the electrons which produce magnetic moments in opposite direction get accelerated.
    Thus, a net magnetic moment is induced in the opposite direction of the applied magnetic field. Hence, the substance is magnetized opposite to the external field.

  • Question 5/5
    1 / -0.33
    If a ferromagnetic material is placed in an external magnetic field then magnetic domains will
    Solutions
    If a ferromagnetic material is placed in an external magnetic field then magnetic domains will may increase or decrease in size because of Atoms of ferromagnetic material in unmagnetized state form domains inside the ferromagnetic material. These domains have large magnetic moments due to the magnetic moment of atoms. In the absence of a magnetic field, these domains have a magnetic moment in different directions. But when the magnetic field is applied, domains aligned in the direction of the field grow in size, and those aligned in the direction opposite to the field reduce in size. Hence, option C is correct.
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