Magnetism

When a magnet approaches a magnetic material, induction occurs first (temporary magnetic poles form in the material due to the magnetic field), and then attraction follows between the induced poles and the magnet's poles. This sequence is fundamental to magnetic phenomena.

Pencil is odd one out as it is non-magnetic.

Nail is odd one out as it is magnetic.

Zinc does not show magnetic properties but the rest of them do show.

Because all magnets are not made of iron, some are made of alloy of aluminium, nickel and cobalt.

A freely suspended bar magnet always aligns itself in the North-South direction because Earth itself acts as a giant magnet. The magnet's north pole points towards geographic North (which is actually magnetic south), and the south pole points towards geographic South. This directional property is why compasses work.

The statement is correctly identified as NOT true. Magnets created by electric current are called electromagnets, NOT diamagnets. Diamagnetism is a completely different property where materials weakly repel magnetic fields (like copper or bismuth). Repulsion IS a better test of magnetism than attraction because any unmagnetized magnetic material will be attracted to a magnet, but only like poles repel.

Magnetism was first discovered in ancient Greece, specifically in the region of Magnesia (hence the name 'magnet'). The Greeks found naturally magnetized stones called lodestones that could attract iron. While India and China also studied magnetism early, Greece is credited with the initial discovery.

A magnetic field is defined as the region around a magnet where its magnetic influence can be detected or felt - where a magnetic material or another magnet would experience force. This field extends beyond just the space between the poles and encompasses the entire 3D space surrounding the magnet.

Iron is the best material for magnetic keepers. A magnetic keeper (or magnet keeper) is a soft iron piece placed across the poles of a horseshoe magnet to preserve its strength. Soft iron has high magnetic permeability, allowing it to provide a low-reluctance path for magnetic flux, preventing self-demagnetization. Stainless steel is not magnetic enough, alnico is already a magnet, and wood is non-magnetic.

All three actions can damage permanent magnets. Heat increases molecular motion, randomizing magnetic domain alignment (Curie temperature). Hammering or dropping physically disrupts the alignment of magnetic domains in the material. All these methods can weaken or completely destroy a permanent magnet's strength.

This is correctly identified as NOT true. The region around a magnet where its effects can be felt is called the magnetic FIELD, not the magnetic pole. Poles are specific points (North and South) at the ends of a magnet where the magnetic force is strongest. The field is the entire region of magnetic influence extending beyond just the poles.

Magnetic compass uses the directional property of magnet whereas the rest use the attractive property of magnet.

Electromagnet is not a permanent magnet. The magnetism is not retained once the current is switched off.

Iron (specifically soft iron) is the best core material for electromagnets. It has very high magnetic permeability, meaning it strongly concentrates magnetic field lines. Iron magnetizes and demagnetizes rapidly when current is turned on/off. Steel retains residual magnetism (becomes permanent), alnico is designed for permanent magnets, and magnetite is a naturally magnetic mineral.