Revision: Magnetism Physics ICSE ICSE Class 6 CISCE

It is a piece of lodestone, which is a black iron oxide (Fe₃ O₄) called magnetite. The word lodestone means a leading stone.

An imaginary line (PQ) bisecting the effective length of a magnet is called the magnetic equator of the magnet.

An imaginary line (XY) passing through the magnetic north pole and magnetic south pole of a bar magnet is called its magnetic axis.

The angle between the horizontal and earth’s magnetic field is known as the angle of dip.

The region around a magnet where its magnetic force can be experienced is called the magnetic field.

Pieces of iron and other magnetic materials which can be made to acquire the properties of natural magnets are called artificial magnets.

lt is a solenoid with a soft iron core placed inside it. When current is passed through the solenoid, the soft iron core becomes a temporary magnet.

The distance (NS) between the north pole and south pole of a magnet is called the length or effective length of the magnet.

The substances which have the property of attracting small pieces of iron, nickel, cobalt, etc, are called magnets, and this property of attraction is called magnetism.

Substances which when placed in a magnetising field are strongly magnetised in the direction of the magnetising field are called ferromagnetic substances.

Substances which when placed in a magnetic field are feebly magnetised in a direction opposite to that of the magnetising field are called diamagnetic substances.

Substances which when placed in a magnetic field are feebly magnetised in the direction of the magnetising field are called paramagnetic substances.

The process of stopping the magnetic field from entering a region is called magnetic shielding.

The number of magnetic field lines crossing unit area kept normal to the direction of field lines is called magnetic flux density. Its unit is Wb/m²

A magnetic field is the region of space around a magnet or a current-carrying conductor within which a magnetic force can be experienced by another magnet or moving charge.

SI Unit: Tesla (T)
Nature: Vector quantity

A magnet is a material that produces a magnetic field and can attract magnetic substances such as iron, nickel, cobalt, and some of their alloys.

The region around a magnet in which it can exert a magnetic force is called its magnetic field.

An electromagnet is a temporary strong magnet made by passing current in a coil wound around a piece of soft iron. It is an artificial magnet.

For ferromagnetic substances above the Curie temperature, the magnetic susceptibility is inversely proportional to (T − T_C), where T_C is the Curie temperature. Mathematically,

On heating beyond the Curie temperature (T_C(iron) = 770 °C), ferromagnetic substances get converted into paramagnetic materials.

The magnetic susceptibility of a paramagnetic material varies inversely with its absolute temperature. Mathematically,

On cooling, paramagnetic substances get converted to ferromagnetic materials at the Curie temperature.

• Diamagnetic substances are weakly repelled and have negative susceptibility.
• Paramagnetic substances are weakly attracted and obey Curie law.
• Ferromagnetic substances are strongly attracted and contain domains.
• Ferromagnets become paramagnetic above the Curie temperature.
• The comparison table is the most important revision tool for board preparation.

• A magnetic field is the region around a magnet or current-carrying conductor where its effect can be detected (shown by the pin/iron-filing activity).
• Oersted (1820) showed that current produces a magnetic effect.
• Faraday introduced the term "magnetic lines of force."
• The magnetic field is a vector quantity; the compass-needle convention gives its direction.
• Significance: electric motors, generators, Earth's magnetism, and electromagnetism as a fundamental force.

• Every ordinary magnet has two poles: north and south.
• Like poles repel; unlike poles attract.
• A freely suspended magnet aligns approximately along the north–south direction.
• Magnetic field lines are closed loops.
• A broken magnet always produces smaller magnets, each with both poles.
• Earth behaves approximately like a giant magnet.
• Near geographic north lies Earth’s magnetic-south region in the simple bar-magnet model.
• A compass works because its needle aligns with Earth’s magnetic field.