Magnetic force
Magnetic force refers to the attraction or repulsion between electrically charged particles, influenced by their motion. This phenomenon is characterized by the creation of magnetic poles, known as north and south poles, where opposite poles attract each other and like poles repel. The understanding of magnetic fields dates back to the thirteenth century, with significant contributions from scientists like Petrus Peregrinus de Maricourt and William Gilbert, who helped establish magnetism as a scientific discipline.
At the atomic level, magnetic force arises from the behavior of electrons and protons, which generate electric fields that exert Coulomb forces on each other. The strength of these fields diminishes with distance. Importantly, magnetic forces can occur when electric currents interact with magnetic fields, such as in the case of permanent magnets. The relationship between magnetic fields and moving charges is described by the Lorentz force law, which quantifies the magnetic force acting on a charge.
Applications of magnetic force are widespread, including in magnets, compasses, and electric motors. Innovative technologies like magnetic levitation trains utilize this force for propulsion, offering a sustainable alternative to traditional fossil-fuel-powered engines by using electromagnetic suspension systems to levitate and propel the train along its path.
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Magnetic force
Magnetic force is the attraction or repulsion of electrically charged particles. It is caused by the motion of these particles, which creates positive and negative poles described as north and south poles. Opposite poles attract (N and S), while like poles repel (N and N or S and S).
The study of magnetic fields dates to the thirteenth century, when Petrus Peregrinus de Maricourt used iron needles to map a magnet's magnetic field. He called the places where the lines crossed the poles. In 1600, English scientist William Gilbert published his findings based on these experiments in a paper called De Magnete. Gilbert, who concluded the earth is a magnet, helped develop magnetism as a science.
Overview
The electric charge in an atom is mostly due to the electrons and protons. Electrons have a negative charge, and protons have a positive charge. These oppositely charged particles attract each other, while same-charged particles repel each other. These protons and electrons create electric fields. These fields exert the Coulomb force—or the attraction or repulsion of the particles because of their electric charge—which radiates outward. The strength of this field decreases with distance, measured as the square of the distance from the source. For example, if point B is three times as far away as point A, the strength of the electric field at point B decreases to one-ninth.
Magnetic force can be generated when magnetic fields and electrical currents interact. Permanent magnets, such as refrigerator magnets, owe their attractive power to the electrical currents of the moving charges at the atomic and subatomic level and the fields these currents generate. Electrical current in a wire is the electrons moving in the wire; electrical current produces a magnetic field. The magnetic force on a moving charge is perpendicular, or at a 90-degree angle, to the velocity of the charge and the direction of the field. This force is often illustrated using Right-Hand Rule #1: Using the right hand, point the index finger left, which is the direction of the velocity of the charge; point the middle finger downward, to represent the direction of the magnetic field; point the thumb upward—this is the direction of the magnetic force. The amount of force a magnetic field exerts on a moving charge is expressed using the Lorentz force law, F=qvB, where F is the magnetic force, q is the charge, v is the velocity, and B is the magnetic field.
Magnetic forces are at work in magnets, compasses, and electric motors. Some roller coasters and trains use magnetic forces, too. Magnetic force has been used to develop high-speed trains that rely on magnetic fields, rather than engines powered by fossil fuels, for propulsion. Maglev trains, or magnetic levitation trains, float over a guideway using a system called electromagnetic suspension (EMS), and they use electromagnetic propulsion systems. Electricity powers metal coils in the guideway system, which generates a magnetic field. This field repels magnets on the undercarriage of the train, causing it to levitate up to 3.9 inches (10 centimeters). Electrified coils in the guideway walls create multiple magnetic fields that constantly reverse polarity to move the train. The magnetic field behind the train repels it, pushing the train forward, while the magnetic field in the front pulls it forward.
Bibliography
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