Olympiad Test: Fun With Magnets -1 - Class 6 MCQ

Magnets attract materials that are magnetic, such as iron and steel. Plain pins are typically made of steel, which is magnetic, so they can be attracted by a magnet. The other materials—wooden pieces, erasers, and pieces of cloth—do not contain magnetic materials and therefore cannot be attracted by a magnet.

A freely suspended magnet always aligns itself in the north-south direction due to the Earth's magnetic field. The magnet's north pole is attracted to the Earth's magnetic south pole, and the south pole of the magnet is attracted to the Earth's magnetic north pole, causing it to align in the north-south direction.

Steel is commonly used to make permanent magnets because it retains its magnetism for a long time. Steel, particularly alloys containing iron, has the ability to be magnetized and maintain its magnetic properties after the external magnetic field is removed. Nickel, aluminium, and iron are also used in various magnetic applications, but steel is specifically preferred for permanent magnets due to its durability in retaining magnetism.

When the north poles of two magnets are placed near each other, they repel each other. This is because like poles of magnets always repel each other, while opposite poles (north and south) attract each other.

When a bar magnet is cut into pieces, each piece will still have both a north pole and a south pole. This happens because cutting the magnet does not destroy its magnetic properties. Instead, it creates smaller magnets, each with its own north and south poles. Therefore, each piece becomes a complete magnet with a north and south pole, not just a single pole.

A magnetic compass is an artificial magnet used to find geographical directions. It consists of a small magnetic needle that aligns itself with the Earth's magnetic field, pointing towards the magnetic north and south poles. This helps in navigation and determining directions.

The magnetic separation is a process in which magnetically susceptible material is extracted from a mixture using magnetic force. This is best way to separate the mixture of sand and iron fillings as iron is attracted by magnet.

We know common pins are made up of stainless steel and steel when brought closer to a magnet or magnetic materials gets attracted towards the magnet and get stick to the magnet. So the common pins will stick all around the magnet as every part of magnet will act as a magnetic material and will attract the pins.

Lead is not suitable for making permanent magnets. Permanent magnets require materials that can retain their magnetization over time, and lead does not have the required magnetic properties. Materials like steel, ticonal, and alnico are suitable for making permanent magnets because they are able to retain their magnetic properties after being magnetized.

A bar magnet has two distinct poles, the north pole (N) and the south pole (S), and these poles are located at the ends of the bar magnet. The orientation of the poles (whether the north pole is on the left or right) depends on how the magnet is placed or aligned, but typically the north pole points towards the Earth's magnetic north. Therefore, while options B and C are possible, the key point is that the poles are located at the ends of the magnet, which makes option A the correct one.

A magnet has two poles: a north pole and a south pole. These are the regions where the magnetic force is strongest. Every magnet, no matter how small or large, always has two poles, and if you cut a magnet in half, each piece will still have two poles (a new north and south pole).

Rainwater is not pure and contains impurities such as dust, pollutants, and minerals suspended in the atmosphere. These impurities can cause rainwater to conduct electricity and potentially affect a magnetic compass, leading to a deflection of the needle. On the other hand, distilled water is supposed to be free of impurities and would not show such effects.

Loadstone (also known as magnetite) is a naturally occurring mineral that has magnetic properties. It is one of the earliest known natural magnets, which occurs in nature without any human intervention.

Wood is a non-magnetic material, meaning it does not interact with magnetic fields. On the other hand, Nickel, Iron, and Cobalt are all magnetic materials and can be attracted by magnets.

The attraction of iron filings by the poles of a magnet is maximum because the magnetic field is strongest at the poles. When iron filings are brought near a magnet, they align themselves along the magnetic field lines, and the effect is most pronounced at the poles, where the magnetic force is greatest.

Placing a copper rod inside a coil carrying a direct current will not magnetise it. Copper is not a magnetic material.

The statements in option B, C, D will magnetise the rod because these actions align the magnetic domains of rod in one direction. So the magnetic property of each domain will effectively get added up. Aligning the magnetic domains is possible in soft iron and steel rods.

So the answer is option A.

The presence of magnetism in a magnet is due to the arrangement of molecules (or more specifically, magnetic domains) within the material. In a magnet, the magnetic domains are aligned in a particular order, which gives rise to a net magnetic field. In an unmagnetized material, these domains are randomly arranged, and their magnetic effects cancel each other out. When the domains are aligned, the material exhibits magnetism.

All of the processes mentioned—casting, pressing and sintering, and extruding—can be used to make magnets, particularly when dealing with different types of magnetic materials, including permanent magnets.

• Casting of magnetic material: This is a process where a magnetic material is melted and poured into a mold to form a magnet shape.
• Pressing and sintering of magnetic material: This involves compacting powdered magnetic material under pressure and then heating it to a high temperature to form a solid magnet. This is common for materials like ferrites and certain types of rare-earth magnets.
• Extruding of magnetic material: This involves forcing a magnetic material through a die to form a shape, such as a wire or rod, which is then magnetized.

Thus, all these processes are used in the production of magnets.

The effective length of a magnet is typically smaller than its geometric length. This is because the effective length is the distance over which the magnetic field is significant, which is usually less than the full length of the magnet. The magnetic field is strongest at the poles and diminishes away from them, so the portion of the magnet that contributes most to the magnetic effect is generally shorter than its total length.

The deflection of the magnetic compass is caused by the magnetic field produced by the current-carrying wire. According to Ampère's Law, the magnetic field around a current-carrying wire is directly proportional to the amount of current flowing through the wire.

As the current in the wire increases, the strength of the magnetic field increases, which in turn increases the deflection of the compass needle. Therefore, if the current in the wire is increased, the deflection of the compass will increase.