Electrons moving along a wire make a magnetic field that goes in circles around the wire. When you bend the wire into a coil, the magnetic fields around each loop of the coil add up to make a long , thin magnet with north at one end and south at the other. The more loops the coil has, the stronger the magnetic field, while the current is flowing. A magnet made from just a coil of wire isn't very strong.
But when you coil the wire around an iron nail, the magnetic domains inside the nail line up and make a strong, temporary magnet. If you disconnect the wire, the magnetic field disappears and the nail is no longer a magnet.
If you leave the wire connected long enough, the nail's magnetic domains will realign enough to make it a permanent magnet. But be careful! The current flowing through the wire makes the wire hot and drains the battery quickly. Explain the relationship between electricity and magnetism. Per Demo or Student: large iron nail about 8 cm 1 metre of insulated copper wire 1 fresh D size battery paper clips or other small magnetic objects tape.
Is the nail itself a magnet? Does it matter if it is connected to the battery? What happens when a wire is coiled around the nail and connected to a battery? What happens when you disconnect the wire? With the rapid rise of electronic devices, the production of electric coils has been required to devote a great number of resources to perfecting and designing electric coils to meet the demand.
Coils for circuit boards are produced from finely wound wire for the production of laminated transformers and toroids. Electric coils designed for wind turbines are capable of meeting the demands of a generator that produces between W to over 1 MW. The coils are made of lightweight materials and insulated for protection against leakage or damage. The purpose of a flowmeter is to measure the volume of a liquid or gas flowing through a pipe. They are used to supply accurate monitoring and control information regarding the flow for precise calculations.
Bobbin mounted flowmeter coils are molded, shaped, and designed to match the radius of the tube where the flow is being measured. Since flowmeter coils are not mechanical, they are not susceptible to wear or abrasion. A basic part of an automobile is an ignition coil that changes the energy from the battery to the thousands of volts required to create a spark in the spark plugs to ignite the fuel for the engine.
As with most coils, ignition coils consist of two sets of copper wires that are wrapped around an iron core. The electric energy from the core is transferred to the distributor and on to the spark plugs. The primary winding of the coil is heavy wire, which is surrounded by secondary windings of lighter smaller wire. The concept of the ignition coil goes back hundreds of years and was adapted for use in the first automobiles. A traffic light sensor is a coil with an inductance meter attached.
When a car enters the field of the inductance meter, it acts like the core of the inductor and changes the inductance of the coil. This lets the traffic light know that a car is present. Transformers have changed the way that electricity is delivered. Initially, all electricity was direct current DC and required a large network of transfer stations to be moved long distances.
With the development of alternating current AC , electricity could be passed over long distances with fewer connecting stations. A key to this development was the transformer. With a transformer, AC could be sent over long distances at high voltage with lower current to avoid loss in the line or wire. The transformer converts the high voltage to low voltage and increases the energy of the current.
Transformers use multiple coils to conduct electricity by the use of electromagnetic flux, which have primary windings on one side and secondary ones on the other side. An electric guitar coil is a form of transducer that converts the vibrations of the strings to electric signals.
The most common form of electric guitar coil is the single coil design as well as dual coils, double coils, or humbucker. With the dual coil design, the pickup has two coils that "buck to hum" and cancel out interference. The pickups, coils, create a magnetic field around the strings of the guitar. Though electric coils are the simplest form of electrical components, they are carefully engineered to fit the applications where they are used.
An electrical coil consists of a core and wiring that is wrapped around the core. Some types of electrical coils do not have a core but just wound wires. The wire and its winding are important aspects of an electrical coil and its performance. The shape and dimensions of the wire used in a coil are chosen to perform a particular function. Inductance, energy loss, strength of insulation, and power of the magnetic field are central determining factors when choosing wiring.
The most efficient coils limit the amount of materials and the volume. There is a ratio between the area of the electrical conductors and the winding space, which is referred to as the fill factor. Round wires will always have some gap, which is increased by the space between layers created by insulation and the number of turns. The fill factor is always less than one and varies between 0. The use of rectangular, square, and flat wires are a method for increasing the fill factor.
There are three types of fill factors, which depend on the ratio between the cross sectional area of the piece and the cross section area of the coil.
The calculation for the fill factor ranges between 0. Dense packing of wires lowers the amount of air space and increases the fill factor. This, in turn, increases the efficiency of an electrical device and improves its conductivity. The best packing of round wires includes having the upper layer of wire fill in the grooves of the lower layer by o of the coil circumference.
Winding wire is an insulated conductor used for interchanging electrical energy with magnetic energy. In most cases, the wire is coated copper or aluminum that has some form of thin layered insulation. When examining such factors as chemical, physical, and mechanical properties, for most electric coils, copper is usually the first choice.
High purity grades of copper are used for applications with high or raised temperatures or for motors that use hydrogen gas for cooling. The diameter, or gauge, of the wire of a coil has two effects. There is a direct relationship between the diameter of the wire and its potential to slot fill or its fill factor.
The second effect is the amount of current that can flow through the coil. The conductor area can easily be increased by using a larger gauge wire that requires less insulation. The problem with increasing the diameter of wire is that it becomes stiffer, less flexible, and more difficult to handle. The stiffness of the wire makes it harder for it to conform to the slot shape, fill factor.
Though it may seem to be more convenient and efficient to use a smaller gauge wire, its use increases the ratio of insulation required. Also, smaller wires increase the number of necessary turns, which can lead to wire damage during insertion. Wires with a 22 to 24 AWG provide a good wire to insulation ratio, can be easily formed, and are readily workable.
When designing a motor, engineers examine the slot opening, slot shape, and the winding as well as the insertion method. Electroplated wires are used in environments where the conditions can deteriorate or damage the wiring.
The materials to plate the wires are gold, silver, and nickel, which come in various thicknesses and are coated with an insulation material. Electroplating offers greater protection in harsh conditions. The plating of the wires significantly improves their properties such as conductivity. Electric coils use a variety of insulation materials that vary according to the temperature range of their application. The types of materials include polyvinyl chloride PVC , polyurethane, polyester, and the different forms of polyimide.
During the winding process, the wires are heated such that the insulation materials bind together. The insulation material enhances the thermal endurance and protects the wire.
The main function of wire insulation is to prevent the wires from touching since it would cause them to short out. Each type of insulation material has different specifications that include thermal capacity, gauge, and application. In some cases, electrical coil wires will have a double coat.
The wire will have an undercoat as an initial cover and a topcoat. This is done to strengthen the wire and increase its durability as well as allowing it to take advantage of the properties of both forms of insulation.
Wires insulated with PVC are able to resist oils, alkali acids, sunlight, weathering, and abrasion. Each of the different types of PVC have different pliability and electrical properties. Polyurethane is an insulation material that is used in harsh and hazardous environments because of its exceptional mechanical properties and high chemical resistance.
Since it is a very flexible material and easily adapted, it is usually used for outdoor applications.
Though it is a strong and sturdy material, it is not normally used for electrical applications. Polyester has a high temperature rating and a very low embrittlement factor. It is highly resistant to abrasions. It has excellent windability, flexibility, and resistance to heat and solvents.
An overcoat of polyamide over polyester improves its windability and thermoplastic flow. Polyimide is one of the most widely used forms of insulation for electromagnetic coils. It has excellent mechanical properties and is able to perform in high temperature applications. Polyimide is a polymer constructed from an imide monomer, which has two acyl groups bonded to nitrogen. The shape, design, and dimensions of a coil winding determines its purpose and function.
The factors that influence a coil winding include inductance, quality factor, strength of the insulation, and the required type of magnetic field to be produced. The structure of the winding depends on the type and geometry of the coil to be wound. Though coil winding can be done in a variety of ways, the basic forms include wild, helical, and orthocyclic. Each of these types are completed by specially designed winding machines. Wild coil winding, or jumble, is characterized by cross winding where the coils are wound unevenly.
The process for wild coil winding is normally used in instances where there is high volume production. Winding is completed at very high speeds and is used for relay coils, small transformers, and smaller electrical motors with a 0. The winding is shaped into a helix and used in low voltage windings. The process of helical winding can include a few strands of wire up to over one hundred that are wound continuously parallel to each other. The interaction between the wires is very similar to the construction of a corkscrew with one layer going in one direction and the next going in the opposite direction.
With helical winding, there is a variation in the pitch angle as can be seen in the diagram below. In orthocyclic winding, each layer fits into the grooves of the layer below it, which is considered to be the most optimal method for coil winding.
The pattern of the winding is continuous over every layer with each turn being parallel to the next with a fractional shift between layers. Sandwich windings have a unique configuration where high voltage and low voltage windings set in the same magnetic access with the high voltage unit between two low voltage units, which reduces the leakage flux. This form of winding is usually used in the production of transformers and resembles an assemblage of discs. This Henry coil or helix from the s is composed of over yards of copper wire, wrapped in cotton, then covered in red paint to reinforce the insulation.
In total, this coil weighs 11 lbs and is representative of many of the helices Henry used in his experiments during his time at Princeton. This later, smaller coil uses a different insulation method than the larger coil. This coil uses much thinner wire and only weights about 2lbs, but contains a similar length of wire as the larger coil.
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