NASA&NIBIRU 2012 video affects me most .that video tells about end day of the world .you can find that video on google search ,I don’t know that is true or fake . but now …………….what can I say???????????? Any how enjoy your remaining days…… if it is true we are the last breed of our worldddddd…………………………… dont miss anyone who all are in your life..............
Thursday, 1 March 2012
Tuesday, 28 June 2011
COMPRESSED AIR ELECTROMAGNETIC ENGINE
INTRODUCTIONTHIS IS MY SECOND PROJECT FOR THE FUTURE ENGINE .
New Proposal For New Engine .
THE ABOVE PICTURES ARE MY NEW IDEA FOR FUTURE ENGINE . IN THIS ENGINE HAVING TWO ELECTROMAGNET`S THOSE TWO ARE WORKS WHEN THE PISTON IN THE TDC , AT THAT TIME COMPRESSED AIR WILL ALLOW TO PASS THE CURRENT FROM ONE SIDE TO ANOTHER SIDE SO THAT ELECTOR MAGNET`S ARE ACTIVE . NOW REPULSIVE FORCE WILL MOVE THE PISTON TO BOTTOM. NOW THE COMPRESSION RATIO WILL DECREASED SO PASSING CURRENT WILL STOP . THIS ACTION WILL REPEATS.......
Monday, 11 April 2011
Current (I) through a wire produces a magnetic field (B). The field is oriented according to the right-hand rule.An electric current flowing in a wire creates a magnetic field around the wire (see drawing below). To concentrate the magnetic field, in an electromagnet the wire is wound into a coil, with many turns of wire lying side by side. The magnetic field of all the turns of wire passes through the center of the coil, creating a strong magnetic field there. A coil forming the shape of a straight tube (a helix) is called a solenoid; a solenoid that is bent into a donut shape so that the ends meet is called a toroid. Much stronger magnetic fields can be produced if a "core" offerromagnetic material, such as soft iron, is placed inside the coil. The ferromagnetic core magnifies the magnetic field to thousands of times the strength of the field of the coil alone, due to the high magnetic permeability μ of the ferromagnetic material. This is called a ferromagnetic-core or iron-core electromagnet.The direction of the magnetic field through a coil of wire can be found from a form of the right-hand rule. If the fingers of the right hand are curled around the coil in the direction of current flow (conventional current, flow of positive charge) through the windings, the thumb points in the direction of the field inside the coil. The side of the magnet that the field lines emerge from is defined to be the north pole.The main advantage of an electromagnet over a permanent magnet is that the magnetic field can be rapidly manipulated over a wide range by controlling the amount of electric current. However, a continuous supply of electrical energy is required to maintain the field.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.
Sturgeon's electromagnet, 1824Danish scientist Hans Christian Ørsted discovered in 1820 that electric currents create magnetic fields. British scientist William Sturgeon invented the electromagnet in 1824. His first electromagnet was a horseshoe-shaped piece of iron that was wrapped with about 18 turns of bare copper wire (insulated wire didn't exist yet). The iron was varnished to insulate it from the windings. When a current was passed through the coil, the iron became magnetized and attracted other pieces of iron; when the current was stopped, it lost magnetization. Sturgeon displayed its power by showing that although it only weighed seven ounces (roughly 200 grams), it could lift nine pounds (roughly 4 kilos) when the current of a single-cell battery was applied. However, Sturgeon's magnets were weak because the uninsulated wire he used could only be wrapped in a single spaced out layer around the core, limiting the number of turns. Beginning in 1827, US scientist Joseph Henry systematically improved and popularized the electromagnet.By using wire insulated by silk thread he was able to wind multiple layers of wire on cores, creating powerful magnets with thousands of turns of wire, including one that could support 2,063 lb (936 kg). The first major use for electromagnets was in telegraph sounders.The magnetic domain theory of how ferromagnetic cores work was first proposed in 1906 by French physicist Pierre-Ernest Weiss, and the detailed modern quantum mechanical theory of ferromagnetism was worked out in the 1920s by Werner Heisenberg, Lev Landau, Felix Bloch and others.Uses of electromagnetsElectromagnets are very widely used in electric and electromechanical devices, including:§ Magnetic separation of material§ Industrial lifting magnets§ Electromagnetic suspension used for MAGLEV trainsFor definitions of the variables below, see box at end of article.The magnetic field of electromagnets in the general case is given by Ampere's Law:which says that the integral of the magnetizing field H around any closed loop of the field is equal to the sum of the current flowing through the loop. Another equation used, that gives the magnetic field due to each small segment of current, is the Biot-Savart law. Computing the magnetic field and force exerted by ferromagnetic materials is difficult for two reasons. First, because the strength of the field varies from point to point in a complicated way, particularly outside the core and in air gaps, where fringing fields and leakage flux must be considered. Second, because the magnetic field B and force are nonlinear functions of the current, depending on the nonlinear relation between B and H for the particular core material used. For precise calculations, computer programs that can produce a model of the magnetic field using the finiteelement method are employed.Magnetic circuit – the constant B field approximation
Magnetic field (green) of a typical electromagnet, with the iron core Cforming a closed loop with two air gaps G in it. Most of the magnetic field Bis concentrated in the core. However some of the field lines BL, called the "leakage flux", do not follow the full core circuit and so do not contribute to the force exerted by the electromagnet. In the gaps G the field lines spread out beyond the boundaries of the core in "fringing fields" BF. This increases the "resistance" (reluctance) of the magnetic circuit, decreasing the total magnetic flux in the core. Both the leakage flux and the fringing fields get larger as the gaps are increased, reducing the force exerted by the magnet. Line L shows the average length of the magnetic circuit, used in equation below. It is the sum of the length Lcore in the iron core and the length Lgap in the air gapsIn many practical applications of electromagnets, such as motors, generators, transformers, lifting magnets, and loudspeakers, the iron core is in the form of a loop or magnetic circuit, possibly broken by a few narrow air gaps. This is because iron presents much less "resistance" (reluctance) to the magnetic field than air, so a stronger field can be obtained if most of the magnetic field's path is within the core.Since most of the magnetic field is confined within the outlines of the core loop, this allows a simplification of the mathematical analysis. See the drawing at right. A common simplifying assumption satisfied by many electromagnets, which will be used in this section, is that the magnetic field strength B is constant around themagnetic circuit and zero outside it. Most of the magnetic field will be concentrated in the core material (C). Within the core the magnetic field (B) will be approximately uniform across any cross section, so if in addition the core has roughly constant area throughout its length, the field in the core will be constant. This just leaves the air gaps (G), if any, between core sections. In the gaps the magnetic field lines are no longer confined by the core, so they 'bulge' out beyond the outlines of the core before curving back to enter the next piece of core material, reducing the field strength in the gap. The bulges (BF) are called fringing fields. However, as long as the length of the gap is smaller than the cross section dimensions of the core, the field in the gap will be approximately the same as in the core. In addition, some of the magnetic field lines (BL) will take 'short cuts' and not pass through the entire core circuit, and thus will not contribute to the force exerted by the magnet. This also includes field lines that encircle the wire windings but do not enter the core. This is called leakage flux. Therefore the equations in this section are valid for electromagnets for which:1. the magnetic circuit is a single loop of core material, possibly broken by a few air gaps2. the core has roughly the same cross sectional area throughout its length.3. any air gaps between sections of core material are not large compared with the cross sectional dimensions of the core.4. there is negligible leakage fluxThe main nonlinear feature of ferromagnetic materials is that the B field saturates at a certain value, which is around 1.6 teslas (T) for most high permeability core steels. The B field increases quickly with increasing current up to that value, but above that value the field levels off and becomes almost constant, regardless of how much current is sent through the windings. So the strength of the magnetic field possible from an iron core electromagnet is limited to 1.6–2 T.Magnetic field created by a currentThe magnetic field created by an electromagnet is proportional to both the number of turns in the winding, N, and the current in the wire, I, hence this product, NI, in ampere-turns, is given the name magnetomotive force. For an electromagnet with a single magnetic circuit, of which length Lcore is in the core material and length Lgap is in air gaps, Ampere's Law reduces to:
is the permeability of free space (or air); note that A in this definition is amperes.
This is a nonlinear equation, because the permeability of the core, μ, varies with the magnetic field B. For an exact solution, the value of μ at the B value used must be obtained from the core material hysteresis curve. If B is unknown, the equation must be solved by numerical methods. However, if the magnetomotive force is well above saturation, so the core material is in saturation, the magnetic field will be approximately the saturation value Bsat for the material, and won't vary much with changes in NI. For a closed magnetic circuit (no air gap) most core materials saturate at a magnetomotive force of roughly 800 ampere-turns per meter of flux path.For most core materials, .
So in equation above, the second term dominates. Therefore, in magnetic circuits with an air gap, the strength of the magnetic field B depends strongly on the length of the air gap, and the length of the flux path in the core doesn't matter much
Magnetic momentA magnet's magnetic moment (also called magnetic dipole moment, and usually denoted μ) is a vector that characterizes the magnet's overall magnetic properties. For a bar magnet, the direction of the magnetic moment points from the magnet's south pole to its north pole, and the magnitude relates to how strong and how far apart these poles are. In SI units, the magnetic moment is specified in terms of A·m2.
A magnet both produces its own magnetic field and it responds to magnetic fields. The strength of the magnetic field it produces is at any given point proportional to the magnitude of its magnetic moment. In addition, when the magnet is put into an external magnetic field, produced by a different source, it is subject to a torque tending to orient the magnetic moment parallel to the field. The amount of this torque is proportional both to the magnetic moment and the external field. A magnet may also be subject to a force driving it in one direction or another, according to the positions and orientations of the magnet and source. If the field is uniform in space, the magnet is subject to no net force, although it is subject to a torque.
A wire in the shape of a circle with area A and carrying current I is a magnet, with a magnetic moment of magnitude equal to IA.
The magnetization of a magnetized material is the local value of its magnetic moment per unit volume, usually denoted M, with units A/m. It is a vector field, rather than just a vector (like the magnetic moment), because different areas in a magnet can be magnetized with different directions and strengths (for example, because of domains, see below).
A good bar magnet may have a magnetic moment of magnitude 0.1 A·m2 and a volume of 1 cm3, or 1×10−6 m3, and therefore an average magnetization magnitude is 100,000 A/m. Iron can have a magnetization of around a million amperes per meter. Such a large value explains why iron magnets are so effective at producing magnetic fields.
Two models for magnets: magnetic poles and atomic currents
Field of a cylindrical bar magnet calculated with Ampère's model
See also: Magnetic moment#Magnetic dipolesAlthough for many purposes it is convenient to think of a magnet as having distinct north and south magnetic poles, the concept of poles should not be taken literally: it is merely a way of referring to the two different ends of a magnet. The magnet does not have distinct north or south particles on opposing sides. If a bar magnet is broken into two pieces, in an attempt to separate the north and south poles, the result will be two bar magnets, each of which has both a north and south pole.
Gilbert model: However, a version of the magnetic pole approach is used by professional magneticians to design permanent magnets. In this approach, the pole surfaces of a permanent magnet are imagined to be covered with so-called magnetic charge, north pole particles on the north pole and south pole particles' on the south pole, that are the source of the magnetic field lines. If the magnetic pole distribution is known, then outside the magnet the pole model gives the magnetic field exactly. In the interior of the magnet this model fails to give the correct field (see #Units and calculations, below). This pole model is also called the Gilbert model of a magnetic dipole.
Ampère model: Another model is the Ampère model, where all magnetization is due to the effect of microscopic, or atomic, circular bound currents, also called Ampèrian currents throughout the material. For a uniformly magnetized cylindrical bar magnet, the net effect of the microscopic bound currents is to make the magnet behave as if there is a macroscopic sheet of electric current flowing around the surface, with local flow direction normal to the cylinder axis. (Since scraping off the outer layer of a magnet will not destroy its magnetic field, it can be seen that this is just a model, and the tiny currents are actually distributed throughout the material). The right-hand rule tells which direction the current flows. The Ampère model gives the exact magnetic field both inside and outside the magnet. It is usually difficult to calculate the Ampèrian currents on the surface of a magnet, whereas it is often easier to find the effective poles for the same magnet.
Magnetic materialsThe term magnet is typically reserved for objects that produce their own persistent magnetic field even in the absence of an applied magnetic field. Only certain classes of materials can do this. Most materials, however, produce a magnetic field in response to an applied magnetic field; a phenomenon known as magnetism. There are several types of magnetism, and all materials exhibit at least one of them.
The overall magnetic behavior of a material can vary widely, depending on the structure of the material, and particularly on its electron configuration. Several forms of magnetic behavior have been observed in different materials, including:
- Ferromagnetic and ferrimagnetic materials are the ones normally thought of as magnetic; they are attracted to a magnet strongly enough that the attraction can be felt. These materials are the only ones that can retain magnetization and become magnets; a common example is a traditional refrigerator magnet. Ferrimagnetic materials, which include ferrites and the oldest magnetic materials magnetite and lodestone, are similar to but weaker than ferromagnetics. The difference between ferro- and ferrimagnetic materials is related to their microscopic structure, as explained below.
- Paramagnetic substances such as platinum, aluminium, and oxygen are weakly attracted to a magnet. This effect is hundreds of thousands of times weaker than ferromagnetic materials attraction, so it can only be detected by using sensitive instruments, or using extremely strong magnets. Magnetic ferrofluids, although they are made of tiny ferromagnetic particles suspended in liquid, are sometimes considered paramagnetic since they cannot be magnetized.
- Diamagnetic means repelled by both poles. Compared to paramagnetic and ferromagnetic substances, diamagnetic substances such as carbon, copper, water, and plastic are even more weakly repelled by a magnet. The permeability of diamagnetic materials is less than the permeability of a vacuum. All substances not possessing one of the other types of magnetism are diamagnetic; this includes most substances. Although force on a diamagnetic object from an ordinary magnet is far too weak to be felt, using extremely strong superconducting magnets diamagnetic objects such as pieces of lead and even mice can be levitated so they float in mid-air. Superconductors repel magnetic fields from their interior and are strongly diamagnetic.
Magnetization and demagnetizationFerromagnetic materials can be magnetized in the following ways:
- Heating the object above its Curie temperature, allowing it to cool in a magnetic field and hammering it as it cools. This is the most effective method, and is similar to the industrial processes used to create permanent magnets.
- Placing the item in an external magnetic field will result in the item retaining some of the magnetism on removal. Vibration has been shown to increase the effect. Ferrous materials aligned with the Earth's magnetic field and which are subject to vibration (e.g., frame of a conveyor) have been shown to acquire significant residual magnetism. A magnetic field much stronger than the Earth's can be generated inside a solenoid by passing direct current through it.
- Stroking: An existing magnet is moved from one end of the item to the other repeatedly in the same direction.
- Heating a magnet past its Curie temperature; the molecular motion destroys the alignment of the magnetic domains. This always removes all magnetization.
- Hammering or jarring: the mechanical disturbance tends to randomize the magnetic domains. Will leave some residual magnetization.
- Placing the magnet in an alternating magnetic field with an intensity above the materials coercivity and then either slowly drawing the magnet out or slowly decreasing the magnetic field to zero. This is the principle used in commercial demagnetizers to demagnetize tools and erase credit cards and hard disks, and degaussing coils used to demagnetize CRTs.
Medical issues and safety
Because human tissues have a very low level of susceptibility to static magnetic fields, there is little mainstream scientific evidence showing a health hazard associated with exposure to static fields. Dynamic magnetic fields may be a different issue however; correlations between electromagnetic radiation and cancer rates have been postulated due to demographic correlations.
If a ferromagnetic foreign body is present in human tissue, an external magnetic field interacting with it can pose a serious safety risk.
A different type of indirect magnetic health risk exists involving pacemakers. If a pacemaker has been embedded in a patient's chest (usually for the purpose of monitoring and regulating the heart for steady electrically induced beats), care should be taken to keep it away from magnetic fields. It is for this reason that a patient with the device installed cannot be tested with the use of an MRI, which is a magnetic imaging device.
Children sometimes swallow small magnets from toys; and this can be hazardous if two or more magnets are swallowed, as the magnets can pinch or puncture internal tissues; one death has been reported.