[Physics Class Notes] on Bar Magnet Pdf for Exam

A Bar Magnet is a Magnet made of ferroMagnetic substances. FerroMagnetic substances give the Magnet its property of Magnetism. As the name suggests, a Bar Magnet is a rectangular piece of the Magnet which, like other Magnets when suspended freely, aligns itself along the Magnetic field of the earth. As it is common knowledge that opposite poles of a Magnet attract and like poles repel each other, similarly while aligning itself to the earth’s Magnetic field, a Bar Magnet follows the same rule.

The Reaction of a Magnet to Iron

Bar Magnets or say any Magnet attracts Iron due to the impact coming from their Magnetic field on that Iron. Before entering the Magnetic field, the polarisation of the Iron atoms inside a piece of Iron is random. After it gets exposed to the Magnetic field, the atoms start to bring into line their electrons according to the flow of the Magnetic field lines, which in turn results in Magnetising the Iron as well. Which, therefore, results in an attraction between the Magnets and the piece of Iron. This is the reason why when a piece of Iron is exposed to a Magnet it starts acting as a Magnet for some time.

Types of Bar Magnet

A Bar is found to exist in two forms:

• Cylindrical Magnet

• Rectangular Magnet

While the structural differences are not that prominent, a Bar Magnet with round edges is called a cylindrical Magnet and the one with sharp and clear edges is called a rectangular Magnet.

Essentially, both forms are known as a Bar Magnet due to their resemblance to a shape of a block, whose one side is longer than the adjacent side, commonly referred to as a ‘Bar’.

The Ways to Make a Bar Magnet Stronger Than Before

All you need to get your hands on is a very strong Magnet. The only step that needs to be done afterward is to repeatedly rub it crossways on your deteriorated Magnet. The Magnet that is stronger will help in realigning the Magnetic fields inside that of the deteriorated Magnet. Another common method used to charge a weak Magnet is Magnet stacking, all you need to do is stack a couple of Magnets together along with the weak one for some time. This will result in similarly realigning the Magnetic fields inside that of the deteriorated Magnet.

Bar Magnet Magnetic Field

The Magnetic field can be defined as the vector value that affects the Magnetic substances, electric charges, and currents that come in its contact.

As can be seen from the above-illustrated diagrams:

• A Magnetic field line moves from the North Pole of the Bar Magnet to the South Pole. The arrows show the direction of the Magnetic lines of force.

• The lines are dense around the poles, symbolising the strength of the Magnetic field which is greatest at the poles.

• The lines are far apart in the middle of the Magnet symbolising the weak Magnetic field around the centre of the Magnet as compared to the poles.

• The attraction between the two opposite poles of two different Magnets is observed as it allows the flow of Magnetic fields from the North Pole to the South Pole.

• While the two Magnets experience an attractive force when the opposite poles are made to enter the other one’s Magnetic field, the same cannot be said when the like poles are made to cross the other one’s Magnetic field.

• Since the two same poles of different Magnets are unable to create the flow of Magnetic lines as needed for the Magnetic field to be formed, repulsive force is experienced by both the Magnets.

Difference between ElectroMagnets and Bar Magnets

• Though ElectroMagnets and Bar Magnets have been proved to have similar Magnetic fields, given below are the differences between them:

• Most Bar Magnets are shaped like blocks of ferroMagnetic constituents whereas ElectroMagnets are coils of wire which are at times enclosed by a ferroMagnetic core in the canter. ElectroMagnets act just like Bar Magnets after an electric current is made to pass through them.

• Bar Magnets produce a Magnetic field of their own whereas ElectroMagnets rely on the outside sources of current for producing a Magnetic field.

• Bar Magnets have a naturally occurring constant Magnetic as they are said to be permanent Magnets, ElectroMagnets on the other hand do not have a continuous Magnetic force as they behave as Magnets only after an external source of electric currents is passed through them.

• The Magnetic force in a Bar Magnet is the same in strength while in an ElectroMagnet it can be changed by the amount of current passed through it.

Properties of Bar Magnet

A Bar Magnet possesses certain properties which are listed below:

• Like other Magnets, a Bar Magnet also has two poles, I. e. the North Pole and the South Pole.  No matter how many times a Bar Magnet is broken, or how small or large the Magnet is, it will always have two poles.

• The Magnetic force of a Bar Magnet gets stronger as we move towards the poles, and gets weaker in the middle of the Magnet.

• When kept together, the opposite pole of the two Bar Magnets will experience attractive force while if the like poles come in contact they will repel each other.

• They remain and act such for their lifetime so as not lose their Magnetism over time.

• Bar Magnets are strongest at both the poles and get weak in the centre part of it.

• When suspended freely in the environment, the North Pole of the Bar Magnet points toward the South Pole of the earth, and the South Pole of the Bar Magnet faces toward the North Pole, and as a result, aligns itself with Earth’s Magnetic field.

• The Bar Magnet attracts iron, steel, and other ferroMagnetic substances which come in contact with its Magnetic field.