Coil

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For other uses, see Coil (disambiguation).

A coil is a series of loops. A coiled coil is a structure where the coil itself is in turn also looping.

Contents

  • 1 General applications
  • 2 Electromagnetic coils
    • 2.1 Analysis
    • 2.2 Coil examples
  • 3 Chemistry, biology and medicine
  • 4 In Ceramics (Fine Arts)
  • 5 External links

[edit] General applications

A helical spring.

A coil is made up of materials, usually rigid, which can be fashioned into a spiral or helical shape. Flexible materials like wire, rope, hose, cable or paper can also be coiled into empty loops, or wound around a central drum or spindle.

Some common applications of coils include:

[edit] Electromagnetic coils

Diagram of typical transformer configurations

An electromagnetic coil (or simply a "coil") is formed when a conductor (usually a solid copper wire) is wound around a core or form to create an inductor or electromagnet. One loop of wire is usually referred to as a turn, and a coil consists of one or more turns. For use in an electronic circuit, electrical connection terminals called taps are often connected to a coil. Coils are often coated with varnish and/or wrapped with insulating tape to provide additional insulation and secure them in place. A completed coil assembly with taps etc. is often called a winding. A transformer is an electromagnetic device that has a primary winding and a secondary winding that transfers energy from one electrical circuit to another by magnetic coupling without moving parts. The term tickler coil usually refers to a third coil placed in relation to a primary coil and secondary coil. A coil tap is a wiring feature found on some electrical transformers, inductors and coil pickups, all of which are sets of wire coils. The coil tap(s) are points in a wire coil where a conductive patch has been exposed (usually on a loop of wire that extends out of the main coil body). As self induction is larger for larger coil diameter the current in a thick wire tries to flow on the inside. The ideal use of copper is achieved by foils. Sometimes this means that a spiral is a better alternative. Multilayer coils have the problem of interlayer capacitance, so when multiple layers are needed the shape needs to be radically changed to a short coil with many layers so that the voltage between consecutive layers is smaller (making them more spiral like).

[edit] Analysis

The inductance of single-layer coils can be calculated to a reasonable degree of accuracy with the simplified formula

\mu H= \frac{R^2 N^2}{9 R + 10 L}

where microhenries are units of inductance, R is the coil radius (measured in inches to the center of the conductor), N is the number of turns, and L is the length of the coil in inches. The online Coil Inductance Calculator calculates the inductance of any coil using this formula. Higher accuracy estimates of coil inductance require calculations of considerably greater complexity. A layperson's translation is:

\, Inductance^{microhenries} = (radius^2*number of turns^2)/(9*radius + 10*length)

In calculating the distances, one centimeter is equal to 0.393700787 inches and one inch is equal to 2.54 centimeters. The inductance formula uses inches. The relationship between the radius and the circumference of a coil is \, r = c /2 \pi, with r as the radius, c as the circumference, and π (the Greek letter pi) as the constant 3.141. The circumference of a coil can be calculated by c = \pi \cdot d , with d as the diameter of the coil and π as 3.141.

[edit] Coil examples

Nikola Tesla's flat spiral coil.

Some common electromagnetic coils include:

Other applications of coils exist in the field of electromagnetic devices. A coilgun is a type of cannon that uses a series of electromagnetic coils to accelerate a magnetic shell to very high velocities. The filament of an incandescent light bulb has usually the shape of a coiled coil, in order to fit the long filament in a small space.

Further reading
External articles

[edit] Chemistry, biology and medicine

RNA coil on the left and DNA coil on the right.

A chemistry coil is a tube of spiral form, used commonly to cool originating steam of the distillation and thus to condense them in liquid form. In the study of how molecules interact with each other, there are a few specific references to organic coils. During self-assembly, organic elements organize to form this structural pattern. Molecular self-assembly assembles the molecules, without guidance or management from an outside source, into these shapes.

Examples of these structural patterns include:

As an acronym, COIL denotes the Chemical Oxygen Iodine Laser.

In medicine, the Guglielmi Detachable Coil is a platinum coil commonly used in intracranial non-invasive surgery, for the occlusion of brain aneurysms.

[edit] In Ceramics (Fine Arts)

Coiling has been used to shape clay into useful beautiful vessels for many of thousands of years. It ranges from Africa to Greece and from China to New Mexico. They have used this method in a variety of ways. Using the coiling technique, it is possible to build thicker or taller walled vessels, which may not have been possible using earlier methods. The technique lets you control the walls as you build them up and allows you to build on top of the walls to make the vessel look bigger and bulge outward or narrow inward with less danger of collapsing. There are many different ways you can build ceramic objects using the coiling technique.

Coil Construction
  1. Squeezing the clay into a coil or rolling between your hands are two different was to make coils. Using these technqiues, it may prove very diffcult to make a smooth preform due to the uneven pressure applied by your hands and fingers.
  2. When rolling with your hands, use a smooth surface. By spreading your hands (to apply even pressure), gently roll the clay back and forth until you think the preform is of the right thickness.
  3. The roll should be a little thicker than a pencil or pen. Now stack the coils on top of each other.
  4. Now, for strength, force the clay together as hard as you can on the inside of the piece without messing the clay up. Use your fingers and scrape the top coil onto the coil underneath.
  5. While smoothing the inside of the piece hold your other hand on the outside so you don’t damage what you have already done.
  6. If you want a top level, gently turn your piece over and lightly tap it on a smooth surface.
  7. Let it dry.
Slab pottery Construction
How to build it
  1. Large flat pieces of clay are rolled out with a rolling pin. The slabs are cut for the base and walls and are attached together.
  2. Slabs work goes fast but lots of care must be given to make sure that the seams won’t crack, break or pull apart during the drying process.