A report on Magnetic field and Electromagnet

The shape of the magnetic field produced by a horseshoe magnet is revealed by the orientation of iron filings sprinkled on a piece of paper above the magnet.
A simple electromagnet consisting of a coil of wire wrapped around an iron core. A core of ferromagnetic material like iron serves to increase the magnetic field created.  The strength of magnetic field generated is proportional to the amount of current through the winding.
Right hand grip rule: a current flowing in the direction of the white arrow produces a magnetic field shown by the red arrows.
Magnetic field produced by a solenoid (coil of wire). This drawing shows a cross section through the center of the coil. The crosses are wires in which current is moving into the page; the dots are wires in which current is moving up out of the page.
A Solenoid with electric current running through it behaves like a magnet.
Industrial electromagnet lifting scrap iron, 1914
A sketch of Earth's magnetic field representing the source of the field as a magnet. The south pole of the magnetic field is near the geographic north pole of the Earth.
Current (I) through a wire produces a magnetic field (B). The field is oriented according to the right-hand rule.
One of the first drawings of a magnetic field, by René Descartes, 1644, showing the Earth attracting lodestones. It illustrated his theory that magnetism was caused by the circulation of tiny helical particles, "threaded parts", through threaded pores in magnets.
The magnetic field lines of a current-carrying loop of wire pass through the center of the loop, concentrating the field there
Hans Christian Ørsted, Der Geist in der Natur, 1854
The magnetic field generated by passing a current through a coil
Cross section of lifting electromagnet like that in above photo, showing cylindrical construction. The windings (C) are flat copper strips to withstand the Lorentz force of the magnetic field. The core is formed by the thick iron housing (D) that wraps around the windings.
Large aluminum busbars carrying current into the electromagnets at the LNCMI (Laboratoire National des Champs Magnétiques Intenses) high field laboratory.
The most powerful electromagnet in the world, the 45 T hybrid Bitter-superconducting magnet at the US National High Magnetic Field Laboratory, Tallahassee, Florida, USA
A hollow tube type of explosively pumped flux compression generator. The hollow copper tube acts like a single turn secondary winding of a transformer; when the pulse of current from the capacitor in the windings creates a pulse of magnetic field, this creates a strong circumferential current in the tube, trapping the magnetic field lines within. The explosives then collapse the tube, reducing its diameter, and the field lines are forced closer together increasing the field.

An electromagnet is a type of magnet in which the magnetic field is produced by an electric current.

- Electromagnet

Magnetic fields surround magnetized materials, and are created by electric currents such as those used in electromagnets, and by electric fields varying in time.

- Magnetic field
The shape of the magnetic field produced by a horseshoe magnet is revealed by the orientation of iron filings sprinkled on a piece of paper above the magnet.

10 related topics with Alpha

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Animation showing operation of a brushed DC electric motor.

Electric motor

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Electrical machine that converts electrical energy into mechanical energy.

Electrical machine that converts electrical energy into mechanical energy.

Animation showing operation of a brushed DC electric motor.
Cutaway view through stator of induction motor.
Faraday's electromagnetic experiment, 1821
Jedlik's "electromagnetic self-rotor", 1827 (Museum of Applied Arts, Budapest). The historic motor still works perfectly today.
An electric motor presented to Kelvin by James Joule in 1842, Hunterian Museum, Glasgow
Electric motor rotor (left) and stator (right)
Salient-pole rotor
Commutator in a universal motor from a vacuum cleaner. Parts: (A) commutator, (B) brush
Workings of a brushed electric motor with a two-pole rotor and PM stator. ("N" and "S" designate polarities on the inside faces of the magnets; the outside faces have opposite polarities.)
A: shunt B: series C: compound f = field coil
6/4 pole switched reluctance motor
Modern low-cost universal motor, from a vacuum cleaner. Field windings are dark copper-colored, toward the back, on both sides. The rotor's laminated core is gray metallic, with dark slots for winding the coils. The commutator (partly hidden) has become dark from use; it is toward the front. The large brown molded-plastic piece in the foreground supports the brush guides and brushes (both sides), as well as the front motor bearing.
Large 4,500 hp AC induction motor.
A miniature coreless motor
A stepper motor with a soft iron rotor, with active windings shown. In 'A' the active windings tend to hold the rotor in position. In 'B' a different set of windings are carrying a current, which generates torque and rotation.

Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate force in the form of torque applied on the motor's shaft.

Field magnets - The magnets create a magnetic field that passes through the armature. These can be electromagnets or permanent magnets. The field magnet is usually on the stator and the armature on the rotor, but in some types of motor these are reversed.

A magnet made of alnico, a ferromagnetic iron alloy, with its keeper

Ferromagnetism

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Basic mechanism by which certain materials form permanent magnets, or are attracted to magnets.

Basic mechanism by which certain materials form permanent magnets, or are attracted to magnets.

A magnet made of alnico, a ferromagnetic iron alloy, with its keeper
Electromagnetic dynamic magnetic domain motion of grain-oriented electrical silicon steel
Kerr micrograph of metal surface showing magnetic domains, with red and green stripes denoting opposite magnetization directions
Moving domain walls in a grain of silicon steel caused by an increasing external magnetic field in the "downward" direction, observed in a Kerr microscope. White areas are domains with magnetization directed up, dark areas are domains with magnetization directed down.

Permanent magnets (materials that can be magnetized by an external magnetic field and remain magnetized after the external field is removed) are either ferromagnetic or ferrimagnetic, as are the materials that are noticeably attracted to them.

Ferromagnetism is very important in industry and modern technology and is the basis for many electrical and electromechanical devices such as electromagnets, electric motors, generators, transformers, and magnetic storage such as tape recorders, and hard disks, and nondestructive testing of ferrous materials.

A "horseshoe magnet" made of alnico, an iron alloy. The magnet, made in the shape of a horseshoe, has the two magnetic poles close together. This shape creates a strong magnetic field between the poles, allowing the magnet to pick up a heavy piece of iron.

Magnet

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A "horseshoe magnet" made of alnico, an iron alloy. The magnet, made in the shape of a horseshoe, has the two magnetic poles close together. This shape creates a strong magnetic field between the poles, allowing the magnet to pick up a heavy piece of iron.
Magnetic field lines of a solenoid electromagnet, which are similar to a bar magnet as illustrated below with the iron filings
Iron filings that have oriented in the magnetic field produced by a bar magnet
Field of a cylindrical bar magnet computed accurately
Hard disk drives record data on a thin magnetic coating
Magnetic hand separator for heavy minerals
Magnets have many uses in toys. M-tic uses magnetic rods connected to metal spheres for construction.
A stack of ferrite magnets
Ovoid-shaped magnets (possibly Hematine), one hanging from another
Field lines of cylindrical magnets with various aspect ratios

A magnet is a material or object that produces a magnetic field.

An electromagnet is made from a coil of wire that acts as a magnet when an electric current passes through it but stops being a magnet when the current stops.

(left) Eddy currents ( I, red ) within a solid iron transformer core. (right) Making the core out of thin laminations parallel to the field ( B, green ) with insulation between them reduces the eddy currents. In this diagram the field and currents are shown in one direction, but they actually reverse direction with the alternating current in the transformer winding.

Magnetic core

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(left) Eddy currents ( I, red ) within a solid iron transformer core. (right) Making the core out of thin laminations parallel to the field ( B, green ) with insulation between them reduces the eddy currents. In this diagram the field and currents are shown in one direction, but they actually reverse direction with the alternating current in the transformer winding.
Typical EI Lamination.
Ferrite rods are simple cylinders of ferrite that can be wound around.
A toroidal core
On the left, a non-adjustable ferrite rod with connection wires glued to the ends. On the right, a molded ferrite rod with holes, with a single wire threaded through the holes.
A ferrite ring on a computer data cable.

A magnetic core is a piece of magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, generators, inductors, magnetic recording heads, and magnetic assemblies.

Eddy currents ( I, red ) induced in a conductive metal plate (C) as it moves to the right under a magnet (N). The magnetic field ( B, green ) is directed down through the plate. The Lorentz force of the magnetic field on the electrons in the metal induces a sideways current under the magnet.  The magnetic field, acting on the sideways moving electrons, creates a Lorentz force opposite to the velocity of the sheet, which acts as a drag force on the sheet.  The blue arrows are counter magnetic fields generated by the circular motion of the charges.

Eddy current

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Eddy currents ( I, red ) induced in a conductive metal plate (C) as it moves to the right under a magnet (N). The magnetic field ( B, green ) is directed down through the plate. The Lorentz force of the magnetic field on the electrons in the metal induces a sideways current under the magnet.  The magnetic field, acting on the sideways moving electrons, creates a Lorentz force opposite to the velocity of the sheet, which acts as a drag force on the sheet.  The blue arrows are counter magnetic fields generated by the circular motion of the charges.
(left) Eddy currents ( I, red ) within a solid iron transformer core. (right) Making the core out of thin laminations parallel to the field ( B, green ) with insulation (C) between them reduces the eddy currents. Although the field and currents are shown in one direction, they actually reverse direction with the alternating current in the transformer winding.
A cross section through a linear motor placed above a thick aluminium slab. As the linear induction motor's field pattern sweeps to the left, eddy currents are left behind in the metal and this causes the field lines to lean.
Lamination of magnetic cores in transformers greatly improves the efficiency by minimising eddy currents
E-I transformer laminations showing flux paths. The effect of the gap where the laminations are butted together can be mitigated by alternating pairs of E laminations with pairs of I laminations, providing a path for the magnetic flux around the gap.
Eddy current brake. The North magnetic pole piece (top) in this drawing is shown further away from the disk than the South; this is just to leave room to show the currents. In an actual eddy current brake the pole pieces are positioned as close to the disk as possible.

Eddy currents (also called Foucault's currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magnetic field.

They can be induced within nearby stationary conductors by a time-varying magnetic field created by an AC electromagnet or transformer, for example, or by relative motion between a magnet and a nearby conductor.

An illustration of a solenoid

Solenoid

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An illustration of a solenoid
Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines
Figure 1: An infinite solenoid with three arbitrary Ampèrian loops labelled a, b, and c. Integrating over path c demonstrates that the magnetic field inside the solenoid must be radially uniform.
The picture shows how Ampère's law can be applied to the solenoid
Magnetic field line and density created by a solenoid with surface current density
Examples of irregular solenoids (a) sparse solenoid, (b) varied pitch solenoid, (c) non-cylindrical solenoid

A solenoid is a type of electromagnet formed by a helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field.

Magnetic circuit

Magnetic circuit

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Made up of one or more closed loop paths containing a magnetic flux.

Made up of one or more closed loop paths containing a magnetic flux.

Magnetic circuit

The flux is usually generated by permanent magnets or electromagnets and confined to the path by magnetic cores consisting of ferromagnetic materials like iron, although there may be air gaps or other materials in the path.

Magnetic circuits are employed to efficiently channel magnetic fields in many devices such as electric motors, generators, transformers, relays, lifting electromagnets, SQUIDs, galvanometers, and magnetic recording heads.

Finding the direction of the cross product by the right-hand rule

Right-hand rule

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Common mnemonic for understanding orientation of axes in three-dimensional space.

Common mnemonic for understanding orientation of axes in three-dimensional space.

Finding the direction of the cross product by the right-hand rule
Conventional direction of the axis of a rotating body
Left-handed coordinates on the left, right-handed coordinates on the right.
Left- and right-handed screws
Prediction of direction of field (B), given that the current I flows in the direction of the thumb
Finding direction of magnetic field (B) for an electrical coil
Illustration of the right-hand rule on the ninth series of the Swiss 200-francs banknote.

Electromagnet: The magnetic field around a wire is quite weak. If the wire is coiled into a helix all the field lines inside the helix point in the same direction and each successive coil reinforces the others. The advance of the helix, the non-circular part of the current and the field lines all point in the positive z direction. Since there is no magnetic monopole, the field lines exit the +z end, loop around outside the helix, and reenter at the −z end. The +z end where the lines exit is defined as the north pole. If the fingers of the right hand are curled in the direction of the circular component of the current, the right thumb points to the north pole.

It reveals a connection between the current and the magnetic field lines in the magnetic field that the current created.

Sharp hysteresis loop of a Schmitt trigger

Hysteresis

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Ehysteresis.PNG

Ehysteresis.PNG

Sharp hysteresis loop of a Schmitt trigger
Elastic hysteresis of an idealized rubber band. The area in the centre of the hysteresis loop is the energy dissipated due to internal friction.

For example, a magnet may have more than one possible magnetic moment in a given magnetic field, depending on how the field changed in the past.

Magnetically soft (low coercivity) iron is used for the cores in electromagnets.

A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet.

Superconductivity

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A magnet levitating above a high-temperature superconductor, cooled with liquid nitrogen. Persistent electric current flows on the surface of the superconductor, acting to exclude the magnetic field of the magnet (Faraday's law of induction). This current effectively forms an electromagnet that repels the magnet.
A high-temperature superconductor levitating above a magnet
"Top: Periodic table of superconducting elemental solids and their experimental critical temperature (T). Bottom: Periodic table of superconducting binary hydrides (0–300 GPa). Theoretical predictions indicated in blue and experimental results in red."
Electric cables for accelerators at CERN. Both the massive and slim cables are rated for 12,500 A. Top: regular cables for LEP; bottom: superconductor-based cables for the LHC
Cross section of a preform superconductor rod from abandoned Texas Superconducting Super Collider (SSC).
Behavior of heat capacity (cv, blue) and resistivity (ρ, green) at the superconducting phase transition
Heike Kamerlingh Onnes (right), the discoverer of superconductivity. Paul Ehrenfest, Hendrik Lorentz, Niels Bohr stand to his left.
Timeline of superconducting materials. Colors represent different classes of materials:

Superconductivity is a set of physical properties observed in certain materials where electrical resistance vanishes and magnetic flux fields are expelled from the material.

Superconducting magnets are some of the most powerful electromagnets known.