Revision: Properties of a Magnetic Field Science SSC (English Medium) 7th Standard Maharashtra State Board

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.

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

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.

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

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

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.

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

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 line joining all the places on globe, having same angle of dip or inclination is called isoclinic line.

A line that joins all the places on earth, having the same angle of declination is called an isogonic line.

The magnetic field lines are the lines drawn in a magnetic field along which a north magnetic pole would move. The magnetic field lines are also known as magnetic lines of force.

A line which joins all the places on earth, having zero angle of declination is called agonic line.

The path in a magnetic field in which a unit north pole tends to move when allowed to do so is known as magnetic field lines of 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.

• 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.