Magnetic Dipole
A magnetic dipole is a configuration in which two equal but opposite magnetic charges are separated by a distance, creating a magnetic field with distinct north and south poles. This phenomenon can be observed at both atomic levels and in larger objects, such as bar magnets and the Earth's magnetic field, which is generated between its North and South Poles. Magnetic dipoles are essential for the functioning of various devices, from basic compasses to advanced technologies like MRI machines in healthcare.
The strength of a magnetic dipole is quantified by the magnetic dipole moment, which depends on the magnetic field's strength and the distance between the poles. Despite their size, small magnets can exert substantial forces due to this dipole moment. In industrial applications, magnetic dipoles are often created using two magnets held apart to generate a controlled magnetic field. They play a crucial role in aligning materials responsive to magnetism and are used in erasing computer hard drives to prevent data theft. Additionally, in medical imaging, magnetic dipoles facilitate the alignment of protons in the body, enabling detailed imaging through MRI technology.
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Magnetic Dipole
A magnetic dipole results from having two equal but opposite magnetic charges separated from each other but still near each other. This causes the magnetic current to flow in a loop at a regular rate. Magnetic dipoles often exist at atomic levels but can be much larger; a bar magnet can be an example of a larger magnetic dipole because it has opposing poles that are separated by some distance. Another example is the magnetic dipole that exists between Earth's North and South Poles and forms the planet's magnetic field. In this case, the distance separating the poles is quite large. Magnetic dipoles allow devices as simple as a compass and as complex as a magnetic resonance imaging (MRI) machine to function.
Background
A magnet is an object that exerts a force that draws objects made of certain metals to it. Magnets can occur naturally; it is believed that the Greeks first observed that natural iron-based stones called lodestones could attract other metals. Metals most likely to form magnets include iron, steel (which is made of iron), nickel, and cobalt.
Magnets have two poles, or ends, that generate opposing charges. These are generally designated as north and south. Alternatively, they may be referred to as north-seeking and south-seeking poles. Placing two magnets with opposite charged poles together will result in the magnets moving toward each other. On the other hand, placing the magnets together in such a way so that both north poles or both south poles face each other will cause the magnets to repel each other.
Each magnetic object is dipolar, meaning it has two poles. Although scientists have created some magnet-like objects with single poles, a true magnet has two poles. If a magnet were cut into pieces, each piece would have its own north and south poles.
The magnetic current flows from one pole and is attracted to the other pole, generally from the south, or negative, pole, to the north, or positive, pole. This creates a loop of current known as the magnetic dipole. These loops of current are invisible to the human eye but can be visualized by placing a bar magnet—a straight length of magnetized material—in the middle of scattered iron filings. The magnetic field will pull the fillings, forming lines around the magnet that reflect the magnetic dipole loops.
Overview
Often when objects exert a force the amount of force is related to the size of the object. That is not always the case with magnetic dipoles; a small magnet can exert a very large force. How much force a magnet can produce is called the magnetic dipole moment, or sometimes the magnetic moment. It is calculated by determining the strength of the field generated and the distance between the two poles. This measurement of strength and distance is called a vector.
In addition to occurring in nature in magnetized rocks and the poles of planets, magnetic dipoles are created and used for industrial purposes as well. One of the simplest versions of this is found in a compass. A compass uses a small magnet encased in a labeled device that allows it to indicate north and to show directional positions relative to north.
Sometimes in industrial uses, the magnetic dipole is formed by using two magnets held a short distance apart. In this case, the magnetic loop is generated in the space between the magnets. These types of dipoles use metal frames often made of steel to hold the magnets a set distance apart. This distance is precisely calculated to result in a magnetic dipole moment that will consistently produce a magnetic field of the desired strength. These dipole devices will also often incorporate some form of shielding to protect the magnetic field from outside sources of magnetic energy and to protect the rest of the device from the effects of the dipole's magnetism.
Devices manufactured to include a magnetic dipole are used to help control or align other materials that respond to magnetic forces. For example, they can be used to align pieces of metal or other magnets that are being used in a product, such as metal fragments that must be formed into a thin film. Magnetic dipoles can also help to direct beams of particles that are responsive to magnetism and can be used to test magnetic sensors used as components in a variety of everyday electronic devices. One common use for magnetic dipoles is erasing the memory of computer hard drives before they are reused or discarded. This protects the former owner from data or identity theft.
Magnetic dipoles are also found in a number of advanced technology devices used in the medical field. Once such piece of technology is the MRI scanner. These devices rely on the natural tendency of protons, the tiny subatomic particles inside every atom, to function as a magnetic dipole. Magnetic dipoles will tend to align with outside sources of magnetism, aligning themselves to nearby magnetic fields. Because of this, the protons in a human body will align with the strong magnet that is part of the MRI scanner. The machine then uses radio frequency waves to "bump" the protons, forcing them to move. As the protons realign to the strong magnet, they release their own radio frequency waves. By taking measurements of these waves, it is possible to create a detailed image of the inside of the human body.
Bibliography
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