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A modern military compass, with included sight device for aligning. A compass is a device that shows the cardinal directions used for navigation and geographic orientation. It commonly consists of a magnetized needle or other element, such as a compass card or compass rose, which can pivot to align itself with magnetic north.
It combined a compass with a protractor built into the base. His design featured a metal compass capsule containing a magnetic needle with orienting marks mounted into a transparent protractor baseplate with a lubber line (later called a direction of travel indicator). By rotating the capsule to align the needle with the orienting marks, the ...
Arago's rotations is an observable magnetic phenomenon that involves the interactions between a magnetized needle and a moving metal disk. The effect was discovered by François Arago in 1824. At the time of their discovery, Arago's rotations were surprising effects that were difficult to explain.
A Flinders bar is a vertical soft iron bar placed in a tube on the fore side of a compass binnacle. The Flinders bar is used to counteract the vertical magnetism inherent within a ship and is usually calibrated as part of the process known as swinging the compass , where deviations caused by this inherent magnetism are negated by the use of ...
Compasses are usually made of metal or plastic, and consist of two "legs" connected by a hinge which can be adjusted to allow changing of the radius of the circle drawn. . Typically one leg has a spike at its end for anchoring, and the other leg holds a drawing tool, such as a pencil, a short length of just pencil lead or sometimes a
The compass's origins may be traced back to the Warring States period (476–221 BC), when Chinese people utilized a device known as a si nan to point in the right direction. During the early Song dynasty, a spherical compass with a small needle made of magnetic steel was created after steady development.
The needle turns to point at a nearby charged object due to charges induced in the ends of the needle by the external charge, through electrostatic induction.For example, if a positively charged object is brought near, the mobile negative charges in the metal will be attracted to it, and move to the end of the needle nearest the object.
While compass surveying, the magnetic needle is sometimes disturbed from its normal position under the influence of external attractive forces. Such a disturbing influence is called as local attraction. [1] The external forces are produced by sources of local attraction which may be current carrying wire (magnetic materials) or metal objects. [2]