What is "induction coil"

Induction \In*duc"tion\, n. [L. inductio: cf. F. induction. See Induct.]

1. The act or process of inducting or bringing in; introduction; entrance; beginning; commencement.

   I know not you; nor am I well pleased to make this time, as the affair now stands, the induction of your acquaintance.
   --Beau. & Fl.

   These promises are fair, the parties sure, And our induction dull of prosperous hope.
   --Shak.

2. An introduction or introductory scene, as to a play; a preface; a prologue. [Obs.]

   This is but an induction: I will draw The curtains of the tragedy hereafter.
   --Massinger.

3. (Philos.) The act or process of reasoning from a part to a whole, from particulars to generals, or from the individual to the universal; also, the result or inference so reached.

   Induction is an inference drawn from all the particulars.
   --Sir W. Hamilton.

   Induction is the process by which we conclude that what is true of certain individuals of a class, is true of the whole class, or that what is true at certain times will be true in similar circumstances at all times.
   --J. S. Mill.

4. The introduction of a clergyman into a benefice, or of an official into a office, with appropriate acts or ceremonies; the giving actual possession of an ecclesiastical living or its temporalities.

5. (Math.) A process of demonstration in which a general truth is gathered from an examination of particular cases, one of which is known to be true, the examination being so conducted that each case is made to depend on the preceding one; -- called also successive induction.

6. (Physics) The property by which one body, having electrical or magnetic polarity, causes or induces it in another body without direct contact; an impress of electrical or magnetic force or condition from one body on another without actual contact.

   Electro-dynamic induction, the action by which a variable or interrupted current of electricity excites another current in a neighboring conductor forming a closed circuit.

   Electro-magnetic induction, the influence by which an electric current produces magnetic polarity in certain bodies near or around which it passes.

   Electro-static induction, the action by which a body possessing a charge of statical electricity develops a charge of statical electricity of the opposite character in a neighboring body.

   Induction coil, an apparatus producing induced currents of great intensity. It consists of a coil or helix of stout insulated copper wire, surrounded by another coil of very fine insulated wire, in which a momentary current is induced, when a current (as from a voltaic battery), passing through the inner coil, is made, broken, or varied. The inner coil has within it a core of soft iron, and is connected at its terminals with a condenser; -- called also inductorium, and Ruhmkorff's coil.

   Induction pipe, Induction port, or Induction valve, a pipe, passageway, or valve, for leading or admitting a fluid to a receiver, as steam to an engine cylinder, or water to a pump.

   Magnetic induction, the action by which magnetic polarity is developed in a body susceptible to magnetic effects when brought under the influence of a magnet.

   Magneto-electric induction, the influence by which a magnet excites electric currents in closed circuits.

   Logical induction, (Philos.), an act or method of reasoning from all the parts separately to the whole which they constitute, or into which they may be united collectively; the operation of discovering and proving general propositions; the scientific method.

   Philosophical induction, the inference, or the act of inferring, that what has been observed or established in respect to a part, individual, or species, may, on the ground of analogy, be affirmed or received of the whole to which it belongs. This last is the inductive method of Bacon. It ascends from the parts to the whole, and forms, from the general analogy of nature, or special presumptions in the case, conclusions which have greater or less degrees of force, and which may be strengthened or weakened by subsequent experience and experiment. It relates to actual existences, as in physical science or the concerns of life. Logical induction is founded on the necessary laws of thought; philosophical induction, on the interpretation of the indications or analogy of nature.

   Syn: Deduction.

   Usage: Induction, Deduction. In induction we observe a sufficient number of individual facts, and, on the ground of analogy, extend what is true of them to others of the same class, thus arriving at general principles or laws. This is the kind of reasoning in physical science. In deduction we begin with a general truth, which is already proven or provisionally assumed, and seek to connect it with some particular case by means of a middle term, or class of objects, known to be equally connected with both. Thus, we bring down the general into the particular, affirming of the latter the distinctive qualities of the former. This is the syllogistic method. By induction Franklin established the identity of lightning and electricity; by deduction he inferred that dwellings might be protected by lightning rods.

Coil \Coil\, n.

1. A ring, series of rings, or spiral, into which a rope, or other like thing, is wound.

   The wild grapevines that twisted their coils from trec to tree.
   --W. Irving.

2. Fig.: Entanglement; toil; mesh; perplexity.

3. A series of connected pipes in rows or layers, as in a steam heating apparatus.

   Induction coil. (Elec.) See under Induction.

   Ruhmkorff's coil (Elec.), an induction coil, sometimes so called from Ruhmkorff, a prominent manufacturer of the apparatus.

n. a transformer that produces a high voltage alternating current pulse from a low voltage direct current supply, especially such a device in the starter motor of an automobile

n. a coil for producing a high voltage from a low-voltage source

An induction coil or "spark coil" ( archaically known as an inductorium or Ruhmkorff coil after Heinrich Ruhmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. To create the flux changes necessary to induce voltage in the secondary coil, the direct current in the primary coil is repeatedly interrupted by a vibrating mechanical contact called an interrupter. Development began in 1836 by Nicholas Callan, Charles Page and others. The induction coil was the first type of transformer and they were widely used in x-ray machines, spark-gap radio transmitters, arc lighting and quack medical electrotherapy devices from the 1880s to the 1920s. Today their only common use is as the ignition coils in internal combustion engines and in physics education to demonstrate induction.

The term 'induction coil' is also used for a coil carrying high-frequency alternating current (AC), producing eddy currents to heat objects placed in the interior of the coil, in induction heating or zone melting equipment.