A freshly demagnetized bar magnet is placed in the East-West direction to ensure that

Analyze the question: The question asks why a freshly demagnetized bar magnet is placed East-West.

Concept: Magnets are normally stored along the North-South direction, in line with the earth's magnetic field, so that the earth's field helps keep the molecular magnets (domains) aligned. This stops the magnet from losing its magnetism over time.

In a demagnetized magnet, the molecular magnets are randomly arranged, so they cancel each other out and there is no net magnetism. If the magnet is placed East-West, it lies at right angles to the earth's magnetic field (which runs roughly North-South). The earth's field then has no component along the length of the bar, so it cannot line up the molecular magnets. The magnet stays demagnetized, and its molecular magnets stay randomly arranged.

Check the options:

• A. The molecular magnets remain randomly arranged. This is correct, because the East-West position avoids the earth's aligning influence.
• B. The molecular magnets are properly aligned. This is wrong, because a demagnetized magnet is not aligned.
• C. It is affected by the earth's magnetic field. This is the opposite of the purpose.
• D. The magnetic domains are within the earth's field. This would cause alignment, which is not what we want.

Answer: The East-West placement prevents the earth's field from magnetizing the bar, so the molecular magnets remain randomly arranged.

Exam tip: Remember "N-S keeps the magnetism, E-W keeps it demagnetized." Magnets are stored N-S (with keepers) to preserve their strength. A demagnetized one is placed E-W so it stays demagnetized.