How to use Magnetic needle in a sentence
C. Oersted's discovery that a magnetic needle is acted on by a voltaic current.
The magnetic needle may be cemented horizontally across the back of a little plane or concave mirror, about or $ in.
C. Oersted (1777-1851) had shown that a magnetic needle is deflected by an electric current, he attempted, in the laboratory of the Royal Institution in the presence of Humphry Davy, to convert that deflection into a continuous rotation, and also to obtain the reciprocal effect of a current rotating round a magnet.
Thus there must in general be a difference between the observer's magnetic meridian - answering to the mean position of the magnetic needle at his station - and the direction the needle would have at a given hour, if undisturbed by the aurora, at any spot where the phenomena which the observer sees as aurora exist.
We may likewise conclude that this conflict performs circles round the wire, for without this condition it seems impossible that one part of the wire when placed below the magnetic needle should drive its pole to the east, and when placed above it, to the west."Advertisement
This discovery, which gained him the Copley medal of the Royal Society in 1825, was followed by another, that a rotating plate of copper tends to communicate its motion to a magnetic needle suspended over it ("magnetism of rotation").
This work, which embodied the results of many years' research, was distinguished by its strict adherence to the scientific method of investigation by experiment, and by the originality of its matter, containing, as it does, an account of the author's experiments on magnets and magnetical bodies and on electrical attractions, and also his great conception that the earth is nothing but a large magnet, and that it is this which explains, not only the direction of the magnetic needle north and south, but also the variation and dipping or inclination of the needle.
There is reason to believe that Gunter was the first to discover (in 1622 or 1625) that the magnetic needle does not retain the same declination in the same place at all times.
In one form of Blondel's oscillograph, the vibrating system is a small magnetic needle carrying a mirror, but the principle on which it operates is the same as that of the instrument above described.
One of the most important parts to check is the floating dial, which contains the magnetic needle.Advertisement
Cardinal Jacques de Vitry, bishop of Acon in Palestine, in his History (cap. 89), written about the year 1218, speaks of the magnetic needle as "most necessary for such as sail the sea"; 1 and another French crusader, his contemporary, Vincent de Beauvais, states that the adamant (lodestone) is found in Arabia, and mentions a method of using a needle magnetized by it which is similar to that described by Kibdjaki.
Faraday first succeeded by the simple but ingenious device of using a light magnetic needle tethered flexibly to the bottom of a cup containing mercury so that one pole of the magnet was just above the surface of the mercury.