Magnetism Formula, Definition, Concepts, Examples

Magnetism is a fascinating and fundamental natural phenomenon that has intrigued humans for centuries. According to their inherent characteristics, it is the force that makes various materials attract or repel one another. The study of magnetism has played a crucial role in shaping our understanding of the universe and has led to various technological advancements that impact our daily lives.

The interaction between a magnet and an iron object is one of the most typical instances of magnetism. This interaction demonstrates two important properties of magnets: attraction and repulsion. Opposite poles of magnets (north and south) attract each other, while like poles repel each other. This behavior is governed by the fundamental law of magnetism known as the law of poles.

What Is a Magnetic Field?

A magnetic field is a region of space where magnetic forces are applied to moving electrical charges, charged particles, or other magnets. Along with the electromagnetic force and gravity, it is one of the basic forces of nature. Electric charges that are moving, such as those produced by current flowing through a wire or by the motion of electrons within atoms, produce magnetic fields.

Magnetic fields have both magnitude and direction, and they can be visualized using field lines. These lines show the way a magnet's north-seeking pole would point if it were placed in the field. The strength of the magnetic field is indicated by the density of these lines, with closer lines indicating a stronger field.

Also Read - Thermodynamics Formula

Some Important Formulas

1. Magnetic Field Inside a Solenoid:

The magnetic field ( B) inside an ideal solenoid (a long, tightly wound coil of wire) is proportional to the current ( I) and the number of turns per unit length ( n) of the solenoid.

Formula: B=µ ₀ n I

Where,

• B is the magnetic field strength inside the solenoid
• I is the current flowing through the solenoid
• n is the number of turns per unit length of the solenoid
• µ ₀ is the permeability of free space.

2. Magnetic Force on a Moving Charge (Lorentz Force Law):

The magnetic force ( F) on a moving charge ( q) in a magnetic field ( B) is perpendicular to both the velocity ( v) of the charge and the magnetic field.

Formula: F=q v B sin(θ)

Where,

• F is the magnetic force
• q is the charge of the particle
• v is the velocity of the particle
• B is the magnetic field strength
• θ is the angle between the velocity and the magnetic field direction

3. Magnetic Force on a Current-Carrying Wire (Lorentz Force Law):

The magnetic force F on a current-carrying wire I in a magnetic field B is directly proportional to the current, the length of the wire L and the magnetic field.

Formula: F= I L B  sin(θ)

Where,

• F is the magnetic force
• I is the current flowing through the wire
• L is the length of the wire segment
• B is the magnetic field strength
• θ is the angle between the wire and the magnetic field direction.

4. Magnetic Field on the axis of the solenoid:

B=µ ₀ nl/2(cos θ ₁ - cos θ ₂ )

5. Magnetic field due to a straight wire:

B=µ _{0 ^/} 4𝜋 1/r  (sin θ ₁ + sin θ ₂ )

Also Read - Ray Optics Formula

Why Magnetic fields are essential

In many disciplines of science and technology, magnetic fields are essential:

1. Electromagnetism: Moving electric charges, such as current flowing through a wire, create a magnetic field around the wire. Conversely, a changing magnetic field can induce an electric current in a nearby conductor, which is the basis of electromagnetic induction.
2. Magnets: Permanent magnets, like those found in refrigerator doors, generate their own magnetic fields due to the alignment of the spins of their electrons.
3. Earth's Magnetic Field: The Earth itself has a magnetic field, often referred to as the geomagnetic field. This field is important for navigation and protection against harmful solar radiation.
4. Medical Imaging: Magnetic fields are used in techniques like magnetic resonance imaging (MRI) to create detailed images of the internal structures of the human body.
5. Electric Motors and Generators: These devices rely on the interaction between magnetic fields and electrical currents to convert electrical energy into mechanical energy (generators), or the other way around (motors).
6. Particle Accelerators: Particle accelerators, such as those used in high-energy physics research, employ magnetic fields to direct and regulate the motion of charged particles.
7. Data Storage: Magnetic fields are utilized in hard drives and other magnetic storage devices to encode and store digital information.

What Is Electricity?

Energy in the form of electricity is produced when charged particles, most often electrons, pass through a conductor. It is a basic natural force that powers everything from electrical gadgets to lighting systems to large industrial gear, and it is essential to our daily life.

At the atomic level, electricity is related to the interactions between protons (positively charged particles), neutrons (uncharged particles), and electrons (negatively charged particles) within atoms. Electrons are relatively loosely bound to their atoms and can move from one atom to another under certain conditions. When a material has an excess of electrons, it becomes negatively charged, and when it has a deficiency of electrons, it becomes positively charged.

Electron Movement

Electron movement refers to the behavior and motion of electrons within atoms and molecules. Understanding electron movement is crucial to comprehending various fundamental principles in chemistry, physics, and materials science.

Here are some key points about electron movement:

1. Atomic Structure: In the Bohr model of the atom, electrons are depicted as orbiting the nucleus in discrete energy levels or shells. However, in more accurate models like the quantum mechanical model, electrons are described by wave functions, which represent the probability distribution of finding an electron in a particular region around the nucleus.
2. Energy Levels and Orbitals: Electrons occupy specific energy levels or shells, and within each shell, there are sublevels called orbitals. These orbitals have different shapes and orientations (s, p, d, f) that describe the three-dimensional space around the nucleus where electrons are likely to be found.
3. Electron Cloud: The electron cloud is a term used to describe the probability distribution of electrons around the nucleus. Electrons do not follow neat, predictable paths like planets around the sun; instead, their exact location can only be described in terms of probabilities.
4. Quantum Mechanics: According to the principles of quantum mechanics, electrons do not have well-defined trajectories. Instead, they exist in a state of superposition, meaning they can exist in multiple places simultaneously until measured or observed.
5. Electron Movement in Chemical Reactions: The movement of electrons plays a fundamental role in chemical reactions. When atoms or molecules interact, electrons may be shared, transferred, or redistributed between them. This leads to the formation of new compounds and the breaking of old bonds.

Also Read - Heat Transfer Formula

Difference Between Electricity and Magnetism

Here's an overview of their differences:

Electricity:

1. Charge: Electricity involves the movement or accumulation of electric charges.
2. Interaction: Charged particles, such as electrons and protons, interact with each other through electric forces. Like charges repel each other, and opposite charges attract.
3. Sources: Electric charges can be found in various materials, both conductors (materials that allow easy flow of electric charges, like metals) and insulators (materials that resist the flow of electric charges, like rubber).
4. Conductivity: The flow of electric charges through a conductor is called electric current. It is usually facilitated by the movement of electrons.
5. Effects: Electric currents create various effects, including the generation of heat, light (as in incandescent bulbs), and the operation of electronic devices.

Magnetism:

1. Poles: Magnetism involves the interaction of magnetic poles. There are two types of magnetic poles: north (N) and south (S). Unlike poles attract each other, and like poles repel.
2. Sources: Magnetism can be found in certain materials known as magnets. These materials can be naturally occurring (like lodestone) or artificially created (using methods like stroking or electric current).
3. Magnetic Fields: Magnets create regions around them called magnetic fields. These fields influence other magnets or magnetic materials within their vicinity.
4. Intrinsic Property: Some materials, like iron, nickel, and cobalt, can be magnetized to become permanent magnets or can be temporarily magnetized by exposing them to a magnetic field.
5. Electromagnetism: Moving electric charges also generate magnetic fields, and changing magnetic fields induce electric currents. This close relationship between electricity and magnetism is summarized by Maxwell's equations.