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Define 'retentivity' and 'coercivity' of a ferromagnetic material.

Important Questions on Magnetism and Matter

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A paramagnetic sample showing a net magnetization of 0.8 A m-1, when placed in an external magnetic field of strength 0.8 T, at a temperature 5 K. If the temperature is raised to 20 K, then the magnetization becomes
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The coercivity of a small magnet, where the ferromagnet gets demagnetised is 3×103 A/m. The current required to be passed in a solenoid of length 10 cm and number of turns 100, so that the magnet gets demagnetised when inside the solenoid is
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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials

Statement I : The ferromagnetic property depends on temperature. At high temperature, ferromagnet becomes paramagnet.

Statement II : At high temperature, the domain wall area of a ferromagnetic substance increases. In the light of the above statements, choose the most appropriate answer from the options given below:

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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials
What happens to a ferromagnetic substance heated above Curie temperature?
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Coercivity of a magnet where the ferromagnet gets completely demagnetized is 3×103Am-1. The minimum current required to be passed in a solenoid having 1000 turns per metre, so that the magnet gets completely demagnetized when placed inside the solenoid is
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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials
Explain Curie’s law for a para magnetic substance.
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Electromagnets are made of soft iron because, soft iron has
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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials
Draw hysteresis curve B-H curve for a ferromagnetic substance.
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Above the curie temperature the susceptibility of a ferromagnetic substance varies
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The magnetic susceptibility of a paramagnetic substance at -173 °C is 1.5×10-2. To have the susceptibility 0.5×10-2, the change in temperature in °C is
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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials
The susceptibility of magnetism at 300 K is 1.2×10-15. What will be its susceptibility at 200 K?
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Hysteresis loops for two magnetic materials A  and B are given below:
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These materials are used to make magnets for electric generators, transformer core and electromagnet core. Then it is proper to use:
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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials
Write definition of Curie temperature for ferromagnetic substances.
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Curie temperature is the temperature above which:

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Name the two factors affecting the magnetism of electromagnet.
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Soft iron is used in making electro-magnets. why?
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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials
Define Curie temperature.
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In a ferroelectric material, as the applied field is gradually reduced to zero, the polarization still left is known as
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The figure gives experimentally measured B vs. H variation in a ferromagnetic material. The retentivity, coercivity and saturation, respectively, of the material are:
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Physics>Electricity and Magnetism>Magnetism and Matter>Magnetic Properties of Materials
A paramagnetic material has 1028 atoms m-3. Its magnetic susceptibility at temperature 350 K is 2.8×10-4. Its susceptibility at 300 K is