Magnetic domains at Rogersceugh

We walked out onto Bowness Common behind Rogersceugh Farm and found the compass sculpture. Ferro-magnetic materials contain small magnetic areas called domains. In unmagnetised iron, the domains all point in different directions and cancel each other out so the iron cannot act as a magnet. It is possible to use another magnet to make the domains line up so that they act in unison and make the iron into a magnet. Iron is said to be a soft magnetic material because the domains can be lined up easily but can get knocked back out of line quite easily. Steel is a hard magnetic material because it takes a lot to line up the domains but they stay lined up for longer. So transformer cores are made from soft iron. The alternating current in the primary coil creates an electromagnet that lines the domains up first one way and then the other way - as shown in the photographs. It does this back and forth 50 times a second. If steel were used, the effort of switching the domains would waste too much energy.