Navigation and Seamanship

2.1.2. Working Principle of Magnetic compass

           

         Magnetism is a fundamental physical phenomenon which occurs both naturally and artificially by induction. It is the property of certain metals to attract or repel items of like material or certain other metals; it is also an effect of electrical currents. An object which exhibits the property of magnetism is called a magnet. It can be elongated, as in a bar magnet, shaped like a horse-shoe, or take other forms. The space around each magnet in which its influence can be detected is called its field; this can be pictured as being composed of many lines of force. The lines concentrate at both ends, and poles, of a magnet. Each magnet always has two-no more, no less-areas of opposite polarity; one is termed north and the other south. The Earth itself is a big magnet having north and south poles, but the poles are not exactly aligned with the rotation axis of the Earth. The magnetic compass is working with the principle of Earth’s Magnetic Field and shows the magnetic north and south. The simplest form of compass consists of a magnetized needle free to rotate in a horizontal plane. Such a needle tends to settle in the magnetic meridian.