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Question
In a permanent magnet at room temperature ______.
Options
magnetic moment of each molecule is zero.
the individual molecules have non-zero magnetic moment which are all perfectly aligned.
domains are partially aligned.
domains are all perfectly aligned.
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Solution
In a permanent magnet at room temperature domains are all perfectly aligned.
Explanation:
At room temperature permanent magnet behaves as a ferromagnetic substance for a long period of time.
At room temperature, the permanent magnet retains ferromagnetic property for a long period of time.
The individual atoms in a ferromagnetic material possess a dipole moment as in a paramagnetic material.
However, they interact with one another in such a way that they spontaneously align themselves in a common direction over a macroscopic volume called domain. Thus, we can say that in a permanent magnet at room temperature, domains are all perfectly aligned.
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