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Electrical Aspects
Published in Frank R. Spellman, The Science of Wind Power, 2022
The electromagnet is of great importance in electricity simply because the magnetism can be “turned on” or “turned off” at will. The starter solenoid (an electromagnet) in automobiles and powerboats is a good example. In an automobile or boat, an electromagnet is part of a relay that connects the battery to the induction coil, which generates the very high voltage needed to start the engine. The starter solenoid isolates this high voltage from the ignition switch. When no current flows in the coil, it is an “air core,” but when the coil is energized, a movable soft-iron core does two things. First, the magnetic flux is increased because the soft-iron core is more permeable than the air core. Second, the flux is more highly concentrated. All this concentration of magnetic lines of force in the soft-iron core results in a very good magnet when current flows in the coil. However, soft iron loses its magnetism quickly when the current is shut off. The effect of the soft iron is, of course, the same whether it is movable, as in some solenoids, or permanently installed in the coil. An electromagnet then consists of a coil and a core; it becomes a magnet when current flows through the coil.
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Magnetic energy is the energy associated with magnets. A magnet is a piece of iron, steel, alloy, ore, etc., showing the property of attracting iron or similar materials called magnetic materials. Magnetic field is the region surrounding a magnetic pole, in which the magnetic force due to it is perceived. A magnetic pole is each of the two regions of a magnet from which the magnetic force appears to originate. The strength and direction of the magnetic field (H) is expressed in terms of the magnetic flux density or magnetic induction, symbol (B) defined as the magnetic flux per unit area of a magnetic field perpendicular to the magnetic force. Flux is a measure of the quantity of magnetism, taking into account the strength and extent of the magnetic field. Magnetic permeability is the ratio of magnetic flux density to the magnetizing field.
Magnetic and Electrical Properties
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
Shielding is used either to protect electronic components, for example magnetic lenses in electron microscopes or components of electronic devices, from external magnetic fields or to confine magnetic fields from powerful magnets such as those in MRI machines. One way of doing this is to use a soft magnetic material. The shield acts by providing an alternative path for the magnetic field lines. The shield must be easy to magnetise and have a strong response to the magnetic field. This means it should have a low coercivity and high permeability, that is, a thin, steep hysteresis curve. Widely used materials are nickel–iron alloys. One example is mu-metal., which is 80% Ni, 15.5% Fe, and 4.5% Mo. The alloy is heated to high temperatures to increase the size of the magnetic domains. Most ferromagnetic materials undergo small changes in their shape and dimensions when a magnetic field is applied. This effect can be used in transducers to produce ultrasound waves and is responsible for the hum from transformers. Mu-metal is interesting because its shape and dimensions are virtually unchanged when a magnetic field is applied.
Future of photovoltaic materials with emphasis on resource availability, economic geology, criticality, and market size/growth
Published in CIM Journal, 2023
G. J. Simandl, S. Paradis, L. Simandl
Many of the materials commonly referred to as PV, battery, and magnet raw materials (Figure 3) are currently considered to be critical (Simandl et al., 2021). An excellent example of a magnet critical material is Nd. It is essential for manufacturing high-performance magnets used in wind turbines, electric car drivetrains, and portable computing and communication equipment (e.g., laptops, tablets, smart phones). It is important to realize that if a given material is designated as critical, the law of supply and demand, which prevails under normal (free market) conditions, does not apply. Financial incentives to producers of critical materials are commonly provided by governments, paragovernmental organizations, or major manufacturing companies. Criticality of a given raw material also encourages vertical integration within industry, the formation of joint ventures, and the signing of long-term contractual agreements to protect existing supply chains or to establish new ones. Furthermore, the constraints limiting the development of many deposits containing specialty materials as discussed in the previous section are eliminated or only partially applicable.
Korea’s metal resources recycling research project – valuable recycling
Published in Geosystem Engineering, 2019
Bong-Gyoo Cho, Young-Ju Cho, Jae-chun Lee, Kyoungkeun Yoo
The demand for permanent magnets, such as NdFeB magnets, has increased as smaller electronic devices and more powerful motors become increasingly necessary. These magnets have been applied in many fields, such as motors for hard disks and home appliances, and magnetic generators for magnetic resonance imaging (Yoon, Kim, Chung, Jeon et al., 2015). Most rare earth elements (REE) are imported from China, who provides 97% of the world’s total supply of REE (Jha et al., 2016). Although wastes such as motors containing NdFeB magnets have been collected by the state-owned Korea Electronics Recycling Co., they have been treated as scrap iron.
Hybrid Feedback-Feedforward Fuzzy Control of PEM Fuel Cell Air Feed System with Electromagnetic Field Optimization
Published in IETE Journal of Research, 2022
Mahmoud S. AbouOmar, Yi-Xin Su, Hua-Jun Zhang
An electromagnet is a single polarity magnet (positive or negative) whose a magnetic field generated by the flow of electric current within a conductor. Two different forces exist between electromagnets: attraction and repulsion. The attraction forces exist between electromagnets with opposite polarity, while the repulsion forces exist between electromagnets with similar polarity. For electromagnets, the attraction forces are greater than the repulsion forces by about (5–10%) [24]. EFO algorithm is based on this concept replacing the ratio between the attraction and repulsion forces by the golden ratio.