Wiktor Wise
A magnet that does not rely on electricity is known as a permanent magnet. These magnets do not require an external power source to function and retain their magnetic properties without electricity. They are commonly used in computers, motors, cars, generators, headphones, speakers, sensors, and as refrigerator magnets. Permanent magnets are created by placing a magnetic material, such as iron, steel, nickel, or cobalt, in a strong magnetic field.
| Characteristics | Values |
|---|---|
| Definition | A permanent magnet is a type of magnet that retains its magnetism without the need for an external power source. |
| How it works | The atoms forming materials that can be easily magnetized, such as iron, steel, nickel, and cobalt, are arranged in small units called domains. Each domain acts like a small magnet. When a magnetic material is placed in a strong magnetic field, the individual domains will gradually swing around into the direction of the field, and the material becomes a magnet. |
| Uses | Permanent magnets are used in computers, motors, cars, generators, headphones, speakers, sensors, magnetic strips, and fridge magnets. |
| How it's made | Modern permanent magnets are made of special alloys. The most common families of permanent magnet materials are made out of aluminum-nickel-cobalt (Alnicos), strontium-iron (ferrites, also known as ceramics), and neodymium-iron-boron. |
| Comparison with electromagnets | Unlike electromagnets, permanent magnets do not require electricity to exhibit magnetic properties. Electromagnets can have their magnetic output adjusted by varying the amount of electricity flowing through them. |
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What You'll Learn
A permanent magnet
Permanent magnets are made by placing a magnetic material, such as iron, steel, nickel, or cobalt, in a strong magnetic field. The atoms in these materials are arranged in small units called domains, which act like tiny magnets. When a magnetic material is placed in a strong magnetic field, the domains gradually align with the field, and the material becomes a magnet.
Permanent magnets have a wide range of applications. They are commonly used to attract other magnetic items, such as in magnetic strips and fridge magnets. They are also used in electronic equipment, including computers, motors, cars, generators, headphones, speakers, and sensors. In addition, permanent magnets are used in electric motors and generators, where they convert electrical energy into mechanical energy or vice versa.
Permanent magnets also have applications in medicine. Hospitals use magnetic resonance imaging (MRI) to diagnose problems in patients' organs without invasive surgery. Chemists employ nuclear magnetic resonance to characterize synthesized compounds.
Furthermore, permanent magnets play a crucial role in magnetic levitation transport, or maglev, which suspends, guides, and propels vehicles, especially trains, through electromagnetic force. By eliminating rolling resistance, maglev technology increases efficiency in transportation.
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A temporary magnet
Temporary magnets are different from permanent magnets, which are capable of emitting a magnetic field without the need for any external source of magnetism or electrical power. Permanent magnets are always magnetized and can attract other magnetic items, such as iron, steel, nickel, cobalt, certain alloys, and other magnets (opposite poles attract, while like poles repel). They are commonly used in computers, motors, cars, generators, headphones, speakers, sensors, magnetic strips, and fridge magnets.
On the other hand, temporary magnets are similar to electromagnets, which require electricity to function as magnets. Electromagnets consist of a coil of wire wound around a core material, typically iron or steel. When an electric current passes through the coil, it creates a magnetic field that magnetizes the core. The strength of the magnetic field can be adjusted by changing the amount of electric current flowing through the coil, the number of turns in the coil, and the properties of the core material.
Electromagnets have a wide range of applications, including magnetic separation, lifting heavy objects, electric motors, and magnetic resonance imaging (MRI) machines. They are also used in magnetic levitation transport, or maglev, which suspends, guides, and propels vehicles, especially trains, through electromagnetic force, resulting in increased efficiency.
Magnets, in general, play a crucial role in energy transformation. They can convert energy from one form to another without any permanent loss of their energy. For example, they can transform mechanical energy into electrical energy, as seen in generators, and electrical energy into mechanical energy, as seen in electric motors and loudspeakers.
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A magnetic field
The magnetic field of a permanent magnet is always present, without the need for an external power source. These magnets are made of materials with atoms that have unpaired electron spins, causing them to spontaneously align and create a magnetic field. Metals like iron, cobalt, nickel, and certain steels and alloys are commonly used to create permanent magnets.
Electromagnets, on the other hand, generate a magnetic field when an electric current flows through them. They consist of a coil of wire wound around a core material, typically iron or steel. When an electric current passes through the coil, it creates a magnetic field around the coil and magnetises the core. The strength of the magnetic field can be adjusted by varying the amount of electric current, the number of turns in the coil, and the properties of the core material.
Magnetic fields have a significant impact on our lives. They play a crucial role in various applications, including electric motors, generators, loudspeakers, and magnetic resonance imaging (MRI) machines. In electric motors, the interaction between the magnetic field and the electric current enables the conversion of electrical energy into mechanical energy. Generators work in the reverse way, converting mechanical energy into electrical energy by moving a conductor through a magnetic field.
Additionally, magnetic fields have important implications for life on Earth. The Earth's magnetic field shields us from high amounts of radiation from the sun and prevents our atmosphere from leaking into space.
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Magnetic materials
Ferromagnetic materials, including iron, cobalt, nickel, and their alloys, are the most commonly encountered type in everyday life. They are strongly attracted to magnetic fields and can become permanently magnetized, generating their own persistent magnetic fields. This property is due to the alignment of unpaired electron spins within the material, resulting in a net magnetic moment. Ferromagnetic materials, such as iron, play a crucial role in the Earth's magnetic field and have various applications, from magnets in our refrigerators to electric motors and generators.
Paramagnetic materials, on the other hand, exhibit a weaker attraction to magnetic fields. They possess unpaired electrons, but their spins may not align spontaneously, requiring an external magnetic field to establish order. While paramagnetism is observed in some materials, it is often masked by the stronger diamagnetic behaviour, which is present in all materials.
Diamagnetic materials are characterised by their weak repulsion from magnetic fields. They lack unpaired electrons, and their intrinsic electron magnetic moments do not produce a bulk effect. Instead, the magnetism arises from the electrons' orbital motions, resulting in a tendency to oppose an applied magnetic field.
The magnetic behaviour of a material is influenced by its structure, particularly its electron configuration, and temperature. At high temperatures, thermal motion disrupts the alignment of electron spins, reducing the overall magnetization. Additionally, the shape of the material, the strength and direction of any electric current, and the material's magnetic moment also affect its magnetic field.
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Magnetic induction
A magnet that does not rely on electricity is called a permanent magnet. It is permanently magnetised and does not require an electric current to generate magnetism.
Faraday's law of induction was later mathematically described by James Clerk Maxwell and became known as the Maxwell-Faraday equation. Lenz's law describes the direction of the induced field.
Electrical conductors moving through a steady magnetic field, or stationary conductors within a changing magnetic field, will have circular currents induced within them by induction, called eddy currents. Eddy currents flow in closed loops in planes perpendicular to the magnetic field. They are useful in eddy current brakes and induction heating systems but are undesirable in the metal magnetic cores of transformers and AC motors and generators as they dissipate energy as heat.
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Frequently asked questions
A permanent magnet.
Permanent magnets have a fixed magnetic output and do not require electricity to exhibit magnetic properties. The atoms in materials that can be easily magnetized, such as iron, steel, nickel, and cobalt, are arranged in small units called domains. Each domain acts like a small magnet, and when most of these domains align in the same direction, the material becomes a magnet.
Modern permanent magnets are made of special alloys, with the most common families being aluminum-nickel-cobalt (Alnicos) and neodymium-iron-boron. Permanent magnets are used in computers, motors, cars, generators, headphones, speakers, sensors, and magnetic strips.
Electromagnets only exhibit magnetic properties when electricity is applied to them. The strength of an electromagnet's magnetic field can be controlled by varying the amount of current flowing through the coil, the number of turns in the coil, and the properties of the core material.
