Question

In the below figure, tube A contains copper filings and tube B contains aluminium fillings. If a strong magnet is brought close to the two tubes as shown in the figure, then
$\left( {\text{a}} \right)$ Centre of gravity of tube A moves towards the right
$\left( {\text{b}} \right)$ Centre of gravity of tube B move towards the right

${\text{A}}{\text{.}}$ only (a) is true
${\text{B}}{\text{.}}$ only (b) is true
${\text{C}}{\text{.}}$ Both (a) and (b) are true
${\text{D}}{\text{.}}$ Neither (a) nor (b) is true

Answer 1

Hint: Here we will proceed by defining the phenomena magnetism. Then, we will discuss the magnetic behaviour of copper and aluminium when these are placed in the presence of magnetic fields.

Complete Step-by-Step solution:
Magnetism is a force that attracts magnetic objects, or repels them. This force is mediated by the magnetic fields which permeate different media. By default magnetism is a property of some materials. However, some materials may be magnetised or demagnetised as required.
At the elementary level, magnetism is caused by electrons like an electric current. Electrons have spin, creating a tiny dipole magnet. While balancing these spins the net force is zero. But this infinitesimally low magnetic moment gets high in the case of a large number of unpaired electrons. This creates a perceptible magnetic field around the metal.
Electrical current can also generate magnetic fields, and vice versa. This induces a circular magnetic field around the wire as an electric current passes through a cable. Similarly, putting a magnetic field close to a good electricity conductor, electrical currents begin to flow inside the conductor.
If you have a magnetic field strong enough, then all matter is magnetic. But copper is so weakly magnetic, that without very, very large magnetic fields, we can not observe it. So, even in the presence of a bar magnet we can say that copper isn't magnetic.
Copper is not magnetic itself, but it interacts with magnets and this is very significant. The power plants use this interaction with magnets to produce the energy that we use every day.
Aluminium is non-magnetic in normal circumstances. The lack of magnetism in aluminium can be due to its crystal structure. As it comes in the midst of a magnetic field, as high-quality magnets are thrown down thick aluminum pipes, one will detect the magnetism shades.
Copper is very weakly magnetic and is unable to observe its magnetic behavior even in the presence of strong magnetic fields (those generated using the given bar magnet).
Therefore, the copper filings in tube A will not displace and thus its center of gravity remains at the same position as before the presence of magnetic bar producing a strong magnetic field.
However, in the presence of strong magnetic fields created by the positioned bar magnet, aluminium becomes slightly magnetic.
Thus, the aluminum fillings in tube B will move toward the bar magnet (i.e., to the right) in order to get closer to the magnet and thus its center of gravity will move to the right in the presence of a magnetic bar that produces a strong magnetic field.
So, the statement (a) is false whereas the statement (b) is true.
Hence, option B is correct.

Note- Metals may be classified into three categories which are ferromagnetic, paramagnetic and diamagnetic, depending on the magnetic properties. While magnets attract strongly ferromagnetic metals, they attract only faintly paramagnetic metals. At the other hand, diamagnetic materials show a poor repulsion when positioned near a magnet.