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Question
Answer the following question.
Write three points of differences between para-, dia- and ferromagnetic materials, giving one example for each.
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Solution
Ferromagnetism:
These substances are strongly attracted by a magnetic field. Ferromagnetic substances can be permanently magnetized even in the absence of a magnetic field. These substances move (strongly) towards the strong field region when kept a non-uniform external magnetic field. Some examples of ferromagnetic substances are iron, cobalt, nickel, gadolinium
Paramagnetism:
The substances that are attracted by a magnetic field are called paramagnetic substances. These substances get magnetized in a magnetic field in the same direction but lose magnetism when the magnetic field is removed. Paramagnetic material moves (weakly) towards the weak field region when kept a non-uniform external magnetic field. To undergo paramagnetism, a substance must have one or more unpaired electrons.
Example O2
Diamagnetism:
This is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. It is generally quite a weak effect in most materials, although superconductors exhibit a strong effect. Diamagnetic material moves (very weakly) away from the strong-field region towards the weak field region. Diamagnetic atoms have only paired electrons. Example H2
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In what way is the behaviour of a diamagnetic material different from that of a paramagnetic, when kept in an external magnetic field?
Explain Curie’s law for a paramagnetic substance.
The susceptibility of a paramagnetic material is χ at 27° C. At what temperature its susceptibility be χ/3?
A domain in a ferromagnetic substance is in the form of a cube of side 1 µm. If it contains 8 × 1010 atoms and each atomic dipole has a dipole moment of 9 × 10-24 Am2 then the magnetisation of the domain is ______.
Relative permittivity and permeability of a material are `epsilon_"r"` and `µ_"r"` respectively. Which of the following values of these quantities are allowed for a diamagnetic material?
Nickel shows ferromagnetic property at room temperature. If the temperature is increased beyond curie temperature, then it will show ______.
Assertion: A paramagnetic sample display greater magnetisation (for the same magnetic field) when cooled.
Reason: The magnetisation does not depend on temperature.
S is the surface of a lump of magnetic material.
- Lines of B are necessarily continuous across S.
- Some lines of B must be discontinuous across S.
- Lines of H are necessarily continuous across S.
- Lines of H cannot all be continuous across S.
What is magnetic hysterisis?
State the dimensions of magnetization.
