magnetic needle
 磁針


 Nee·dle n.
 1. A small instrument of steel, sharply pointed at one end, with an eye to receive a thread, -- used in sewing.
 Note: ☞ In some needles (as for sewing machines) the eye is at the pointed end, but in ordinary needles it is at the blunt end.
 2. See Magnetic needle, under Magnetic.
 3. A slender rod or wire used in knitting; a knitting needle; also, a hooked instrument which carries the thread or twine, and by means of which knots or loops are formed in the process of netting, knitting, or crocheting.
 4. Bot. One of the needle-shaped secondary leaves of pine trees. See Pinus.
 5. Any slender, pointed object, like a needle, as a pointed crystal, a sharp pinnacle of rock, an obelisk, etc.
 Dipping needle. See under Dipping.
 Needle bar, the reciprocating bar to which the needle of a sewing machine is attached.
 Needle beam Arch., in shoring, the horizontal cross timber which goes through the wall or a pier, and upon which the weight of the wall rests, when a building is shored up to allow of alterations in the lower part.
 Needle furze Bot., a prickly leguminous plant of Western Europe; the petty whin (Genista Anglica).
 Needle gun, a firearm loaded at the breech with a cartridge carrying its own fulminate, which is exploded by driving a slender needle, or pin, into it. [archaic]
 Needle loom Weaving, a loom in which the weft thread is carried through the shed by a long eye-pointed needle instead of by a shuttle.
 Needle ore Min., acicular bismuth; a sulphide of bismuth, lead, and copper occuring in acicular crystals; -- called also aikinite.
 Needle shell Zool., a sea urchin.
 Needle spar Min., aragonite.
 Needle telegraph, a telegraph in which the signals are given by the deflections of a magnetic needle to the right or to the left of a certain position.
 Sea needle Zool., the garfish.


 Mag·net·ic Mag·net·ic·al a.
 1. Pertaining to the magnet; possessing the properties of the magnet, or corresponding properties; as, a magnetic bar of iron; a magnetic needle.
 2. Of or pertaining to, or characterized by, the earth's magnetism; as, the magnetic north; the magnetic meridian.
 3. Capable of becoming a magnet; susceptible to magnetism; as, the magnetic metals.
 4. Endowed with extraordinary personal power to excite the feelings and to win the affections; attractive; inducing attachment.
    She that had all magnetic force alone.   --Donne.
 5. Having, susceptible to, or induced by, animal magnetism, so called; hypnotic; as, a magnetic sleep. See Magnetism. [Archaic]
 Magnetic amplitude, attraction, dip, induction, etc. See under Amplitude, Attraction, etc.
 Magnetic battery, a combination of bar or horseshoe magnets with the like poles adjacent, so as to act together with great power.
 Magnetic compensator, a contrivance connected with a ship's compass for compensating or neutralizing the effect of the iron of the ship upon the needle.
 Magnetic curves, curves indicating lines of magnetic force, as in the arrangement of iron filings between the poles of a powerful magnet.
 Magnetic elements. (a) Chem. Physics Those elements, as iron, nickel, cobalt, chromium, manganese, etc., which are capable or becoming magnetic. (b) Physics In respect to terrestrial magnetism, the declination, inclination, and intensity. (c) See under Element.
 Magnetic fluid, the hypothetical fluid whose existence was formerly assumed in the explanations of the phenomena of magnetism; -- no longer considered a meaningful concept.
 Magnetic iron, or Magnetic iron ore. Min. Same as Magnetite.
 Magnetic needle, a slender bar of steel, magnetized and suspended at its center on a sharp-pointed pivot, or by a delicate fiber, so that it may take freely the direction of the magnetic meridian.  It constitutes the essential part of a compass, such as the mariner's and the surveyor's.
 Magnetic poles, the two points in the opposite polar regions of the earth at which the direction of the dipping needle is vertical.
 Magnetic pyrites. See Pyrrhotite.
 Magnetic storm Terrestrial Physics, a disturbance of the earth's magnetic force characterized by great and sudden changes.
 magnetic tape Electronics, a ribbon of plastic material to which is affixed a thin layer of powder of a material which can be magnetized, such as ferrite.  Such tapes are used in various electronic devices to record fluctuating voltages, which can be used to represent sounds, images, or binary data.  Devices such as audio casette recorders, videocasette recorders, and computer data storage devices use magnetic tape as an inexpensive medium to store data.  Different magnetically susceptible materials are used in such tapes.
 Magnetic telegraph, a telegraph acting by means of a magnet. See Telegraph.

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 magnetic needle
      n : a slender magnet suspended in a magnetic compass on a
          mounting with little friction; used to indicate the
          direction of the earth's magnetic pole