What Is A Non Permanent Magnet

What is a Non-Permanent Magnet? A Comprehensive Guide

A magnet is an object that produces a magnetic field. This field is invisible, but its effects are readily observable, causing forces on other magnetic materials. Magnets come in two primary varieties: permanent magnets and non-permanent magnets (also known as temporary magnets). While permanent magnets retain their magnetic properties indefinitely, non-permanent magnets only exhibit magnetism under specific conditions. This article will delve deep into the world of non-permanent magnets, exploring their properties, behaviors, and applications.

Understanding Magnetism: The Foundation

Before diving into the specifics of non-permanent magnets, let's establish a basic understanding of magnetism. Magnetism is a fundamental force of nature, arising from the movement of electric charges. At the atomic level, electrons orbit the nucleus and also spin on their own axis, both contributing to the creation of magnetic fields.

In most materials, the magnetic fields of individual atoms cancel each other out, resulting in no net magnetic effect. However, in ferromagnetic materials like iron, nickel, and cobalt, these atomic magnetic fields align, creating a strong collective magnetic field. This alignment can be permanent (in permanent magnets) or temporary (in non-permanent magnets).

Defining Non-Permanent Magnets: Temporary Magnetism

A non-permanent magnet is a material that becomes magnetized only when it is placed within an external magnetic field. Once the external field is removed, the material loses its magnetic properties. This temporary magnetization occurs because the atomic magnetic domains within the material align temporarily with the external field. These domains are small regions within the material where the atomic magnetic moments are aligned. When exposed to an external field, these domains tend to align, creating a net magnetic moment. However, this alignment is not stable, and thermal vibrations disrupt the alignment when the external field is removed.

Key characteristics of non-permanent magnets:

• Temporary Magnetism: They only exhibit magnetic properties in the presence of an external magnetic field.
• Weak Magnetic Field: Their magnetic field strength is typically much weaker than that of permanent magnets.
• Easy Magnetization and Demagnetization: They are easily magnetized and demagnetized.
• Material Dependence: The strength of their temporary magnetism depends heavily on the material's properties, particularly its magnetic permeability. Materials with high permeability are more easily magnetized.

The Role of Magnetic Permeability

Magnetic permeability (μ) is a crucial property that determines a material's ability to support the formation of a magnetic field within itself. High permeability materials readily allow magnetic lines of force to pass through them, making them ideal candidates for temporary magnets. Substances with low permeability resist the formation of magnetic fields. Ferromagnetic materials have high permeability, explaining why many temporary magnets are made from these materials.

Materials Commonly Used for Non-Permanent Magnets

Several materials demonstrate the properties of non-permanent magnetism. Here are some examples:

• Iron: A readily available and inexpensive material, iron exhibits significant temporary magnetism. Its high permeability allows for relatively strong temporary magnetic fields. However, it is also prone to rust, limiting its use in certain applications.

• Steel: Various types of steel, particularly soft steel, are widely used due to their relatively high permeability and improved durability compared to pure iron. The addition of alloying elements alters the steel's magnetic properties, leading to variations in the strength of temporary magnetism.

• Nickel: Another ferromagnetic material, nickel, shows good temporary magnetic characteristics. It offers better corrosion resistance than iron but is often more expensive.

• Some Alloys: Specific alloys are designed for their enhanced magnetic properties. These alloys can be tailored to have specific levels of permeability, making them suitable for particular applications requiring varying levels of temporary magnetism.

How Non-Permanent Magnets Work: Domain Alignment

The behavior of a non-permanent magnet is directly related to the alignment of its magnetic domains. In an unmagnetized state, these domains are randomly oriented, resulting in a net magnetic field of zero. When subjected to an external magnetic field, the domains tend to rotate and align themselves with the external field. This alignment creates a net magnetic moment, making the material temporarily magnetic.

The degree of alignment, and consequently the strength of the temporary magnet, depends on several factors including:

• Strength of the external magnetic field: A stronger external field will induce a higher degree of domain alignment.
• Material properties: The magnetic permeability of the material plays a crucial role. Higher permeability leads to easier alignment.
• Temperature: Higher temperatures increase thermal agitation, hindering domain alignment and weakening the temporary magnetism.

Applications of Non-Permanent Magnets

Despite their temporary nature, non-permanent magnets are essential components in numerous applications. Their ability to be easily magnetized and demagnetized makes them particularly useful in scenarios requiring controlled magnetic fields.

Examples include:

• Electromagnets: Electromagnets are the most common application of non-permanent magnets. An electric current flowing through a coil of wire creates a magnetic field. A ferromagnetic core placed within the coil greatly enhances the magnetic field strength. When the current is switched off, the core loses its magnetism. This principle is used in various applications like cranes, motors, and loudspeakers.

• Magnetic relays and switches: These devices use an electromagnet to control the switching of electrical circuits. The electromagnet temporarily magnetizes a core, causing it to attract an armature and close the circuit.

• Magnetic recording media: Though not directly as a permanent magnet, the principle applies. In magnetic tapes and hard disk drives, data is stored by magnetizing tiny regions on the magnetic material. These regions are temporarily magnetized in different patterns, representing the stored information. The read head detects these magnetized regions to retrieve the data.

• Magnetic levitation (Maglev) trains: While these systems utilize strong electromagnets, the principle of temporary magnetism is crucial. The electromagnets generate temporary magnetic fields that interact with guide rails or tracks, allowing the train to levitate and move with reduced friction.

• Scientific instruments: Various scientific instruments rely on electromagnets to create controllable magnetic fields for experiments and research purposes, such as MRI machines and particle accelerators.

Non-Permanent Magnets vs. Permanent Magnets: A Comparison

Conclusion: The Versatility of Temporary Magnetism

Non-permanent magnets, while not as visually striking as their permanent counterparts, play a critical and often unseen role in many aspects of modern technology. Their unique characteristic of temporary magnetization allows for the precise and controlled manipulation of magnetic fields, making them indispensable components in a wide range of applications. Understanding their properties and behaviors is crucial to appreciating their contribution to the technological advancements we rely on daily. From powering electric motors to enabling data storage, the impact of non-permanent magnets is profound and far-reaching. Continued research and development in materials science will further enhance their capabilities and lead to even broader applications in the future.