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CHAPTER XXI NEGATRONS AND MAGNETISM
Everyone is familiar with the ordinary steel magnet and its attraction for iron. A few simple facts about it may be repeated to refresh the memory of those who may have forgotten.
(1) Steel can be made into a permanent magnet. (2) Soft iron can be magnetized only temporarily. A bar of steel — the blade of a screwdriver, for example — can be magnetized by stroking it against a magnet, or by winding wire around it and passing current from a battery through the wire. A bar of soft iron, such as an iron nail, will also be magnetized when it is surrounded by wire carrying current, but only for so long as the current flows. When the current is turned off the iron loses its magnetic property.
All these facts are as important in electrical work as the fact that copper wire will conduct current. There is one more familiar point of special significance, which is emphasized here in order that it may stand out and not be overlooked or forgotten. It is this:
(3) Any conductor carrying current is a magnet while the current flows, even though there is no iron or steel near it.
Let current from a battery pass through a copper wire and a magnetic attraction will be exerted either upon small bits of iron, or upon a second conductor carrying current.
Magnetic and Static Fields
(4) The attraction and repulsion manifested by negatrons and positrons, described a few pages back, are not magnetic in any way. An electric charge repels its like charge and attracts its opposite. It shows, how
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