22.2 Ferromagnets and Electromagnets
3 min read•june 18, 2024
materials are magnetic powerhouses, exhibiting strong magnetic properties and the ability to retain . These materials, like iron and nickel, have high and permeability, making them crucial for various applications.
play a key role in ferromagnets, aligning when exposed to external fields. The marks a critical point where ferromagnetic properties disappear. harness the electricity-magnetism connection, creating controllable magnetic fields for diverse uses.
Ferromagnetic Materials
Ferromagnets vs other magnetic materials
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- Ferromagnetic materials exhibit strong magnetic properties attract and retain magnetic fields (iron, nickel, cobalt)
- Have high magnetic susceptibility easily by external magnetic fields
- Retain magnetic properties after external is removed
- High magnetic fields pass through easily
- due to alignment of magnetic moments of individual atoms (magnetic dipoles)
Magnetic domains and magnetization
- Magnetic regions within ferromagnetic material where magnetic moments of atoms align in same direction
- Unmagnetized has randomly oriented magnetic domains resulting in net zero magnetic field
- External magnetic field aligns magnetic domains causing material to become magnetized
- Magnetization involves growth of aligned magnetic domains at expense of oppositely aligned domains
- Movement of separating adjacent domains crucial in magnetization process
- Domain walls move to minimize overall magnetic energy of system
- occurs when all domains are aligned, and further increase in external field produces no additional magnetization
Magnetic Properties and Electromagnets
Curie temperature and ferromagnetic properties
- critical temperature above which ferromagnetic material loses ferromagnetic properties
- Above Curie temperature, thermal energy overcomes alignment of magnetic moments, material becomes
- Curie temperature specific to each ferromagnetic material (iron ~1043 K or 770 ℃)
- As temperature approaches Curie point, ferromagnetic properties weaken
- Magnetic susceptibility and permeability decrease
- Spontaneous magnetization gradually disappears
- Curie temperature important for applications determines temperature range material maintains ferromagnetic properties
Electricity-magnetism connection in electromagnets
- Electromagnets based on principle that electric currents generate magnetic fields
- describes relationship between and generated magnetic field
- Magnetic field strength () proportional to current (), inversely proportional to distance () from current:
- In , coil of wire () wound around
- through coil generates magnetic field
- Ferromagnetic core concentrates and enhances magnetic field produced by current
- Magnetic field strength in electromagnet increased by:
- Increasing number of turns in coil
- Increasing electric current flowing through coil
- Using ferromagnetic core with high magnetic permeability
- Electromagnets allow control of magnetic field strength by adjusting electric current
- Creates strong, controllable magnetic fields for applications (electric motors, generators, systems)
Advanced Magnetic Concepts
- describe the fundamental relationships between
- is a type of magnetism where materials exhibit partial alignment of magnetic moments, resulting in weaker magnetization than ferromagnets
- refers to the directional dependence of a material's magnetic properties, influencing the preferred orientation of magnetization
Key Terms to Review (40)
Ampère's Law: Ampère's law is a fundamental principle in electromagnetism that describes the relationship between an electric current and the magnetic field it creates. It establishes a quantitative link between the circular magnetic field generated around a current-carrying conductor and the magnitude of the electric current flowing through it.
Biot-Savart law: The Biot-Savart law describes the magnetic field generated by a steady electric current. It states that the magnetic field at a point in space is proportional to the current element and inversely proportional to the square of the distance from the element.
Biot-Savart Law: The Biot-Savart law is a fundamental principle in electromagnetism that describes the magnetic field generated by an electric current. It provides a mathematical expression to calculate the magnetic field at any point in space due to a current-carrying conductor.
Curie temperature: Curie temperature is the temperature at which a ferromagnetic material loses its permanent magnetic properties and becomes paramagnetic. This temperature marks a phase transition from ferromagnetism to paramagnetism.
Curie Temperature: The Curie temperature, also known as the Curie point, is the critical temperature at which a ferromagnetic or ferrimagnetic material loses its permanent magnetic properties and becomes paramagnetic. This temperature marks the transition from a magnetically ordered state to a magnetically disordered state.
Domain Walls: Domain walls are the boundaries that separate regions of uniform magnetization, known as magnetic domains, within a ferromagnetic material. They play a crucial role in the magnetic properties and behavior of ferromagnets and electromagnets.
Domains: Domains are small, magnetically uniform regions within a ferromagnetic material. Each domain has its own magnetic moment that can align with an external magnetic field.
Electric and magnetic fields: Electric and magnetic fields are two interdependent fields that propagate as waves through space. They form the basis of electromagnetic waves, where oscillations in one field induce oscillations in the other.
Electric current: Electric current is the flow of electric charge through a conductor. It is measured in amperes (A) and represented by the symbol 'I'.
Electric Current: Electric current is the flow of electric charge through a conductive material, such as a wire or a semiconductor. It is a fundamental concept in the study of electricity and is essential for understanding various electrical phenomena and applications.
Electromagnet: An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. Unlike permanent magnets, the magnetic field of an electromagnet can be easily turned on and off, making it a versatile and controllable source of magnetic fields.
Electromagnetic induction: Electromagnetic induction is the process by which a changing magnetic field within a closed loop of wire induces an electromotive force (emf) in the wire. It is a fundamental principle underlying many electrical technologies, such as transformers and electric generators.
Electromagnetism: Electromagnetism is a branch of physics involving electric and magnetic fields and their interactions. It encompasses phenomena such as the force between charges and the behavior of magnets.
Electromagnets: Electromagnets are magnets created by the flow of electric current through a coil of wire, which generates a magnetic field. They can be turned on or off and their strength can be adjusted by changing the current.
Ferrimagnetism: Ferrimagnetism is a type of magnetic ordering found in certain materials, where the magnetic moments of the atoms or ions within the material are aligned in an anti-parallel fashion, but the magnitudes of the moments are unequal, resulting in a net magnetic moment. This magnetic behavior is intermediate between ferromagnetism and antiferromagnetism, and it is responsible for the magnetic properties of various materials, including ferrites.
Ferromagnet: A ferromagnet is a material that can be magnetized and retain its magnetization, even in the absence of an external magnetic field. These materials exhibit strong magnetic properties and are the basis for many technological applications, including permanent magnets, electric motors, and data storage devices.
Ferromagnets are closely related to the topics of 22.2 Ferromagnets and Electromagnets, as they are the fundamental building blocks of these concepts. Understanding the nature and behavior of ferromagnets is essential for comprehending the principles behind the generation and manipulation of magnetic fields.
Ferromagnetic: Ferromagnetic materials are those that exhibit strong magnetic properties due to the alignment of their magnetic domains. Common examples include iron, cobalt, and nickel.
Ferromagnetic Core: A ferromagnetic core is a material, typically made of iron or an iron alloy, that is used to concentrate and amplify the magnetic field produced by an electric current. It is a crucial component in the operation of electromagnets and transformers, as it enhances the efficiency and strength of the magnetic field.
Hans Christian Oersted: Hans Christian Oersted was a Danish physicist who is best known for his discovery of the relationship between electricity and magnetism. His groundbreaking experiment in 1820 demonstrated that an electric current could deflect a magnetic needle, establishing the fundamental connection between these two phenomena and laying the foundation for the field of electromagnetism.
Magnetic Anisotropy: Magnetic anisotropy refers to the directional dependence of a material's magnetic properties. It describes the tendency of a material's magnetic moments to align preferentially along certain crystallographic directions or axes within the material's structure.
Magnetic Dipole: A magnetic dipole is a pair of equal and opposite magnetic poles, typically represented as a small bar magnet or the magnetic moment of an atomic or subatomic particle. It is the fundamental unit of magnetism and is responsible for the generation and behavior of magnetic fields.
Magnetic Domains: Magnetic domains are microscopic regions within a magnetic material where the magnetic moments of atoms are aligned in a common direction. These aligned magnetic moments create small, localized magnetic fields that contribute to the overall magnetization of the material.
Magnetic Field: A magnetic field is a region in space where magnetic forces can be detected. It is a vector field that describes the magnetic influence of electric currents and magnetized materials on the space around them. The magnetic field is a fundamental concept in electromagnetism and is essential for understanding various phenomena in physics, including the behavior of ferromagnets, the motion of charged particles, and the production of electromagnetic waves.
Magnetic field strength inside a solenoid: Magnetic field strength inside a solenoid is the intensity of the magnetic field created within a coil of wire when an electric current passes through it. It is uniform and parallel to the axis of the solenoid.
Magnetic flux: Magnetic flux is the measure of the quantity of magnetism, taking into account the strength and extent of a magnetic field. It is calculated as the product of the magnetic field and the area through which it passes, perpendicular to the field.
Magnetic Flux: Magnetic flux is a measure of the total amount of magnetic field passing through a given surface or area. It represents the strength and distribution of a magnetic field and is a fundamental concept in the study of electromagnetism and its applications.
Magnetic Hysteresis: Magnetic hysteresis is the phenomenon where the magnetic flux density (B) of a ferromagnetic material does not linearly follow the applied magnetic field strength (H), but instead exhibits a lagging or hysteresis effect. This results in the material retaining a residual magnetism even after the external magnetic field is removed.
Magnetic Levitation: Magnetic levitation, or maglev, is a technology that uses magnetic fields to lift and propel an object without physical contact. This phenomenon is achieved by the repulsive and attractive forces between superconducting or permanent magnets, allowing objects to float or move frictionlessly above a surface.
Magnetic Permeability: Magnetic permeability is a measure of the ability of a material to support the formation of a magnetic field within itself. It is a fundamental property that describes the degree of magnetization of a material in response to an applied magnetic field.
Magnetic Saturation: Magnetic saturation is the state in which a ferromagnetic material has been magnetized to its maximum capacity, where further increases in the applied magnetic field produce no significant increase in the material's own magnetic field. This concept is crucial in understanding the behavior of magnets and electromagnets.
Magnetic Susceptibility: Magnetic susceptibility is a measure of the degree to which a material can be magnetized in an external magnetic field. It is a fundamental property that describes the magnetic behavior of a substance and its ability to interact with and respond to magnetic fields.
Magnetization: Magnetization is the process by which a material, such as a magnet or ferromagnetic substance, becomes magnetized. It involves the alignment of the magnetic moments of the atoms or molecules within the material, resulting in the creation of a magnetic field that can interact with other magnetic fields.
Magnetized: Magnetized materials have domains aligned such that they exhibit a net magnetic field. This alignment can be induced by an external magnetic field or occur naturally.
Maxwell's Equations: Maxwell's equations are a set of four fundamental equations that describe the relationships between electric and magnetic fields and electric charges and currents. These equations form the foundation of classical electromagnetism and are essential for understanding various electromagnetic phenomena.
Paramagnetic: Paramagnetic materials are substances that are weakly attracted to an applied magnetic field and lose their magnetic properties when the field is removed. This term is particularly relevant in the context of understanding ferromagnets, electromagnets, and the behavior of magnetic fields and field lines.
Solenoid: A solenoid is a type of electromagnet consisting of a coil of wire wound into a tight spiral. When an electric current flows through the coil, it creates a magnetic field inside the solenoid, which can be used to produce a strong and uniform magnetic field in a specific region of space.
Spontaneous Magnetic Moment: The spontaneous magnetic moment refers to the intrinsic magnetic property of certain materials, such as ferromagnets, where the atoms or electrons within the material possess a natural, non-zero magnetic moment even in the absence of an external magnetic field. This innate magnetic behavior arises from the quantum mechanical spin and orbital angular momentum of the electrons.
Tesla: The tesla (T) is the SI unit of magnetic field strength or magnetic flux density. It measures how much force a magnetic field exerts on moving charges or current-carrying wires.
Tesla: The tesla (T) is the unit of magnetic flux density or magnetic induction in the International System of Units (SI). It is named after the Serbian-American inventor and electrical engineer Nikola Tesla, who made significant contributions to the design of the modern alternating-current (AC) electrical supply system.
Weber: The weber (symbol: Wb) is the unit of magnetic flux in the International System of Units (SI). It is named after the German physicist Wilhelm Eduard Weber. The weber is a fundamental unit that is used to quantify the amount of magnetic flux present in a magnetic field, and it plays a crucial role in understanding various electromagnetic phenomena.