The typical values of leakage factor are approximately from:. The reluctance offered by the magnetic circuit or a part of magnetic circuit does NOT depend upon the:.
A current of 10 A is passing along a straight wire. Now, the wire is bent to form a loop. What should be the diameter of the loop such that the force produced at its centre will be the same as the force produced by the straight conductor at a distance of 0.
Suggested Test Series. Suggested Exams. More Electromagnetic Theory Questions Q1. Calculate the EMF induced in it. Diamagnets in a non-uniform magnetic field shift towards the weaker area of the field. We can say that the magnetic field lines are pushed outside of the field. This is how diamagnetic levitation works.
A relatively strong magnetic field generated by modern magnets makes it possible to levitate not just various diamagnets but also small living organisms, mostly those whose body consists primarily of water.
Scientists from Radboud University Nijmegen in the Netherlands were able to levitate a frog in a magnetic field with a magnetic flux density of about 16 T. NASA researchers levitated a mouse, which is a lot closer biologically to humans than a frog.
They used a magnet based on superconductor technology. When an alternating magnetic field is applied to them, all conductors display diamagnetic properties. This phenomenon is based on the eddy currents also known as Foucault currents, generated within an alternating magnetic field in conductors. They resist the external magnetic field. The interaction between a magnetic field and paramagnets is very different.
The particles of paramagnets such as atoms, molecules, and ions have their own magnetic moment, and they align with the external magnetic field. This creates a resultant magnetic field, which exceeds the original magnetic field of the material in magnitude. Paramagnets include aluminum, platinum, as well as alkali metals and alkaline earth metals such as lithium, cesium, sodium, magnesium, tungsten, and their alloys. Many other substances and elements are also paramagnets, including oxygen, nitrogen oxide, manganous oxide, ferric chloride, and many others.
The magnetic permeability of paramagnets is low, just a little more than one. Paramagnets in a non-uniform magnetic field are attracted to the areas where the magnetic field is stronger. When the effect of the magnetic field is removed, paramagnets do not stay magnetized. This is because the direction of the internal magnetic moments of the particles of paramagnets such as atoms, molecules, and ions is random due to the thermal motion.
Ferromagnets are self-magnetized and thanks to this property they make up the naturally occurring permanent magnets, which are known to us from ancient times. In the past magnets were considered to have magical powers, and were used in various religious rituals, and even in building construction.
The first prototype of the compass was invented by the Chinese explorers in the first—second century BC and was used by our curious ancestors to build houses according to the Feng Shui principles. Actual compasses were used for navigation through deserts along the Silk Road as early as the 11th century.
Later use of compasses in naval navigation was paramount in the development of navigation and in discovering new sea trading routes. Ferromagnetism is a manifestation of the quantum-mechanical properties of electrons, which have a spin that is their own magnetic dipole moment. In other words, electrons are like mini magnets. Each complete electron shell can hold only sets of pairs of electrons with opposite spins.
This is to say that the magnetic field of these electrons is directed in the opposite direction from each other. The cumulative magnetic moment of the atoms with paired electrons is equal to zero, and thus only the atoms with an incomplete electron shell that have unpaired electrons can be ferromagnets.
Ferromagnets include transition metals iron, copper, nickel , rare earth metals gadolinium, terbium, dysprosium, holmium, erbium , and alloys of these metals. Alloys of non-ferromagnets with the above metals are also ferromagnetic, as well as the alloys of chrome and manganese with non-ferromagnets, and some of the metals of the actinide group. The magnetic permeability of ferromagnets is much higher than one. The degree to which they can be magnetized when exposed to an external magnetic field is nonlinear.
Ferromagnets display hysteresis, meaning that when the external magnetic field stops acting upon them they stay magnetized. One has to apply a magnetic field of the opposite direction to demagnetize ferromagnets. The Russian physicist and chemist Alexander Stoletov was a pioneer in researching the properties of ferromagnets.
The curve that represents the dependence between the magnetic permeability and the strength of a magnetic field is named after him. Modern ferromagnets are widely used in science and technology because many devices use magnetic induction. For example, in information technology, they have been used in the first computers.
The random access memory of these first computers had ferrite toroidal cores; the information was also stored on magnetic tapes, floppy disks, and hard drives. The latter are still produced in hundreds of millions per year. Magnetic fields are widely used in modern electrical engineering, primarily in power generation. For example, they are valuable in various electrical generators, voltage transformers, electromagnetic drives of various devices, instruments and mechanisms, in measurement science and technology, in various physical experimental setups, and in surge breaker devices used for protection from electric shock and for emergency shut-downs of electricity.
In the British physicist and mathematician Peter Barlow described a homopolar motor that he invented. It was a prototype of modern DC electric motors. This invention is also very valuable because it was created long before magnetic induction was discovered. Most of the electric motors today use Ampere force, which is applied to a conducting loop in a magnetic field.
This is what makes the motor move. In Faraday created an experimental setup to demonstrate the magnetic induction phenomenon. It had a device now known as a toroidal transformer. The principle of operation used in this transformer is still used in many modern voltage and current transformers, regardless of their power, construction, and usage. In addition to the work above Faraday also showed theoretically and proved experimentally the possibility of converting mechanical motion into electricity.
For this work, he used the homopolar DC generator, which he invented. This generator became the prototype for all DC generators. As for the first alternator, it was created by the French inventor Hippolyte Pixii in Later Ampere suggested adding a commutator, which allowed generation of pulsating DC current. Most generators of electrical energy that use magnetic induction are based on the principle of the generation of electromotive force in a closed circuit that is situated inside an alternating magnetic field.
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