Lorentz Force
The Lorentz force is an electromagnetic force experienced by a charged particle moving through electric and magnetic fields. It is mathematically represented by the equation F = qE + qv x B, where F is the force, q is the charge, E is the electric field, v is the velocity of the particle, and B is the magnetic field. The Lorentz force is always perpendicular to both the velocity of the charged particle and the magnetic field, leading to unique motion patterns. Named after Dutch physicist Hendrik A. Lorentz, this force plays a crucial role in various technologies, including particle accelerators, mass spectrometers, and NASA's pulsed plasma thrusters, which utilize the Lorentz force to maneuver spacecraft. The force also highlights the interplay between electric and magnetic phenomena, as moving charges create magnetic fields, which interact with other charges. Understanding the Lorentz force is essential for grasping the principles of electromagnetism and its applications in modern technology.
On this Page
Subject Terms
Lorentz Force
The Lorentz force is the influence that produces a change in a physical quantity. It is the electromagnetic force F on a charged particle q moving with velocity v through an electric E and magnetic B field: F = qE + qvx B. The magnetic force is perpendicular to the velocity and magnetic field.
The Lorentz force is named for Dutch physicist Hendrik A. Lorentz. He shared a Nobel Prize with one of his students, Pieter Zeeman, for their work on electromagnetic radiation.
The Lorentz force contributes to a number of devices and developments. These include particle accelerators and mass spectrometers. The National Aeronautics and Space Administration (NASA) has used the Lorentz force on plasma to develop pulsed plasma thrusters, which are used to maneuver spacecraft with precision.
Background
The understanding of light, magnetic fields, and electric fields developed through the efforts of many scientists.
Hendrik A. Lorentz, who developed the Lorentz force law, was born in Arnhem, the Netherlands, in 1853. He was a professor and physicist, and he devoted much of his early academic and scientific career to James Clerk Maxwell's theory of electricity and light.
Maxwell developed an electromagnetic theory of light propagation during the nineteenth century. He believed one theory could explain light and both electric and magnetic fields all at once. He built upon the discoveries of Hans Christian Oersted, who sought a relationship between electricity and magnetism, and Michael Faraday, who converted electric energy into magnetic energy. From Faraday's work, Maxwell surmised that electromagnetic waves traveled at the speed of light. He further realized that visible light is a form of electromagnetic radiation. Thanks to Maxwell's 1873 A Treatise on Electricity and Magnetism, Heinrich Hertz was able to create ways to transmit and receive radio pulses. Microwaves and televisions are among the many modern conveniences that rely on these pulses to operate.
Overview
Atoms are made up of protons, neutrons, and electrons. Protons make up the nucleus, or center, of the atom, and have a positive charge. Neutrons are also part of the nucleus, but they have no charge. Unlike protons and neutrons, electrons are not stationary. They are very small and orbit the nucleus. The atom can lose electrons to another material. When this happens, one substance gains electrons and becomes positively charged; the other material, which has lost electrons, becomes negatively charged. An electrically charged atom or molecule is an ion. An example is when a balloon is rubbed against a sweater; the sweater gains electrons and becomes positively charged. Like charges repel, or push away from each other, while unlike charges attract each other. Because the balloon and sweater have unlike charges, the balloon will cling to the sweater. Charged objects also attract uncharged objects, so the charged balloon will also cling to a wall or other uncharged object. This electrostatic force is also called the Coulomb force or Coulomb interaction. According to the law, the electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the separation distance between the objects.
Electrical current is the flow of moving electrons. Because electrons with a negative charge are attracted to a positive charge, the electrons can flow. An electrical current needs a circuit or path for the electrons; a wire, for example, can serve as a circuit for the flow of electrons. An electrical current also needs a power source, such as a battery or generator, and a use for the electricity, such as a lightbulb. When charged particles move, they create magnetic fields. Electrons spin, and usually form pairs, in which one is spin up and the other spin down. Atoms with unpaired electrons can create a directional magnetic field. An electromagnetic (EM) field is generated when the velocity of a charged particle changes.
Magnetism is the physical manifestation of the attraction and repelling due to the positive and negative charges. An electric current traveling through a wire is made of moving charged particles, such as electrons. A magnetic field around the wire is generated by these particles. This field may attract or repel an external magnetic field. When the charge moves through a magnetic field, the Lorentz force occurs. The force is at a 90-degree angle to both the direction of the charge and the direction of the magnetic field. It is a vector force, meaning it has both direction and magnitude or strength. The direction is determined by the electrical charge—two like-charged objects will push away from each other, so their direction will be outward. Magnitude depends on several factors, including the strength of the charges of objects and the distance between them.
The Lorentz force is a pressure created when the lines of the charge and the lines of the magnet repel each other and create pressure on the opposite side of the current and magnet, where the lines are rotating counterclockwise and attracting each other. The force occurs on the side of attraction. This creates a motional electromagnetic force in the magnetic field.
The Lorentz force is created and used in many devices. These include circular path particle accelerators, magnetrons, and mass spectrometers. NASA utilizes the Lorentz force in pulsed plasma thrusters. Plasma is an electrically neutral gas—the positive and negative charges add up to zero. A spark from an energy storage unit (ESU) and electrodes creates plasma (the main discharge), which vaporizes and ionizes the surface of a solid propellant. This becomes a propellant plasma, which due to the Lorentz force is pushed out of the thruster.
Bibliography
"Coulomb's Law." Physics Classroom, www.physicsclassroom.com/class/estatics/Lesson-3/Coulomb-s-Law. Accessed 25 Nov. 2024.
"Lorentz Force Law." Georgia State University HyperPhysics, hyperphysics.phy-astr.gsu.edu/hbase/hframe.html. Accessed 25 Nov. 2024.
Lucas, Jim. "What Is Magnetism? Magnetic Fields & Magnetic Force." Live Science, 2 Feb. 2022, www.livescience.com/38059-magnetism.html. Accessed 25 Nov. 2024.
Mahmud, K., S. Rana, A. Al-Zubaidi, R. Mehmood, and S. Saleem. "Interaction of Lorentz Force with Cross Swimming Microbes in Couple Stress Nano Fluid Past a Porous Riga Plate." International Communications in Heat and Mass Transfer, vol. 138, Nov. 2022, DOI: 10.1016/j.icheatmasstransfer.2022.106347. Accessed 25 Nov. 2024.
"Maxwell's Electromagnetic Theory of Light Propagation." Azo Optics, 16 Sept. 2014, www.azooptics.com/Article.aspx?ArticleID=944. Accessed 25 Nov. 2024.