71. Bar Magnet. A straight magnet is called a bar magnet. Magnetize a sewing-needle. For some experiments a needle-magnet, as we may call it, is better than a large magnet.
72. Bar Magnet. A harness-needle, which is thicker and stronger than a sewing-needle, makes an excellent bar magnet.
73. Bar Magnet. For long slim magnets use a knitting-needle. Some knitting-pins, as they are sometimes called, break off short when bent, but most of them will bend considerably before breaking. These slim magnets are excellent for the study of Consequent Poles. (See text-book.)
74. Flexible Bar Magnets. It is often necessary to have flexible magnets so that they may be bent into different shapes. These may be made from watch or clock springs, as such steel, called spring steel, will straighten out again as soon as the pressure is removed from it. Corset steels, dress steels, hack-saw blades, etc., make good thin flexible bar magnets.
75. Strong Bar Magnets may be made from flat files. The handle end may be broken off so that the two ends of the file shall be nearly alike in size. These should be magnetized upon an electro-magnet.