Magnetism

What is Magnetism?

Magnetism is a physical phenomenon that is associated with the motion of electric charge. It is one of the fundamental forces of nature and gives rise to the attractive and repulsive forces between certain materials, such as magnets.

Magnets have two poles: a North pole and a South pole. Like poles repel each other, and opposite poles attract each other. The Earth itself acts like a giant magnet with its magnetic poles located near the geographic poles.

Magnetic Field

A magnetic field is the region around a magnet where magnetic forces can be felt. It is represented by magnetic field lines that show the direction of the magnetic force.

The strength and direction of a magnetic field at a point can be determined using the magnetic field vector. The unit of magnetic field is the Tesla (T), and the magnetic field is denoted by B.

Magnetic Force

The magnetic force on a moving charge is given by the Lorentz force law. The force acting on a charged particle moving with velocity v in a magnetic field B is given by:

F = q(v × B)

Where:

• F is the magnetic force (in newtons).
• q is the charge of the particle (in coulombs).
• v is the velocity of the particle (in meters per second).
• B is the magnetic field (in teslas).

Magnetic Moment

The magnetic moment is a vector quantity that measures the strength and direction of a magnet's ability to generate a magnetic field. It is given by the product of the pole strength and the distance between the poles.

The magnetic moment of a current-carrying coil is given by:

μ = I × A

Where:

• I is the current flowing through the coil (in amperes).
• A is the area of the coil (in square meters).

Magnetic Materials

Materials can be classified based on their magnetic properties into the following categories:

• Diamagnetic materials: These materials have weak negative magnetism, meaning they are repelled by magnetic fields. Examples: copper, silver, and gold.
• Paramagnetic materials: These materials are weakly attracted by magnetic fields. Examples: aluminum, platinum.
• Ferromagnetic materials: These materials are strongly attracted by magnetic fields and can be permanently magnetized. Examples: iron, nickel, cobalt.

Electromagnetism

Electromagnetism is the interaction of electric currents with magnetic fields. When an electric current flows through a conductor, it generates a magnetic field around the conductor. If the conductor is wound into a coil, the magnetic field becomes stronger, and the coil becomes an electromagnet.

The strength of an electromagnet can be increased by increasing the current, the number of turns in the coil, or the permeability of the material in the core of the electromagnet.

Previous Year Questions

• RRB JE 2016: Which of the following is a characteristic of a ferromagnetic material?
• It can be permanently magnetized and is strongly attracted by a magnetic field.
• SSC JE 2017: What happens when a charged particle enters a magnetic field at an angle of 90 degrees to the field lines?
• The particle will experience the maximum magnetic force and follow a circular path.
• HSSC JE 2018: What is the SI unit of magnetic flux?
• Weber (Wb)

Conclusion

Magnetism plays an important role in understanding the behavior of materials and their interactions with magnetic fields. From the study of magnetic fields to the applications of electromagnetism in modern technology, magnetism is essential for numerous fields, including electronics, engineering, and physics. A solid understanding of magnetism forms the foundation for advanced concepts like electromagnetism, which is the cornerstone of electrical engineering.