Which following statements is TRUE about a permanent magnet?
A. North and south magnetic poles can be separated. B. In a permanent magnet (such as iron), all the atoms act as large, aligned magnets. C. The atomic magnets in different parts of a permanent magnet can point in different directions. D. Cutting a bar permanent magnet produces two new bar magnets and will produce separate north and south poles.
The correct answer and explanation is:
The correct answer is B: In a permanent magnet (such as iron), all the atoms act as large, aligned magnets.
A permanent magnet is a material that retains its magnetism even after the external magnetic field is removed. In materials like iron, cobalt, and nickel, the atoms have magnetic properties due to the alignment of their electron spins, creating tiny atomic magnets, or magnetic dipoles. In a permanent magnet, these atomic magnets are aligned in the same direction, which causes the material itself to become magnetized.
When the atomic magnets in a material are aligned in the same direction, their magnetic fields combine to produce a strong overall magnetic field. This alignment is key to the magnet’s ability to maintain its magnetism over time. The regions where the atomic magnets are aligned are known as magnetic domains. In an unmagnetized piece of material, these domains are randomly oriented, and their magnetic effects cancel out. However, when the material is magnetized, these domains align, and the object becomes a permanent magnet.
Let’s look at why the other options are incorrect:
- A: North and south magnetic poles cannot be separated. In a permanent magnet, even if you break it into pieces, each piece will have both a north and south pole. This is due to the intrinsic nature of magnetic dipoles; you can’t isolate a single pole.
- C: The atomic magnets in different parts of a permanent magnet are aligned. If they pointed in different directions, the material would not be magnetized.
- D: If you cut a bar magnet in half, each piece will still have a north and south pole. The concept of isolating magnetic poles is not physically possible in permanent magnets.
In summary, the key feature of a permanent magnet is that the atomic magnets inside it are aligned in a consistent direction, making the entire material exhibit a strong, lasting magnetic field.