Radio Broadcast (May-Oct 1922)

The Grid QUESTIONS AND ANSWERS The Grid is a Question and Answer Department maintained especially for the radio amateurs. Full answers will be given wherever possible. In answering questions, those of a like nature will be grouped together and answered by one article. Every effort will be made to keep the answers simple and direct, yet fully self-explanatory. Questions should be addressed to Editor, "The Grid," Radio Broadcast, Garden City, N. Y. The letter containing the questions should have the full name and address of the writer and also his station call letter, if he has one. Names, however, will not be published. The questions and answers appearing in this issue are chosen from among many asked the editor in other capacities. IVhat is an electron? IVhy do hot metals throw off electrons? Why will a current pass through a tube only when the filament is lighted? How many electrons pass from the filament to plate in a detector tube? Can an electron he seen with a magnifying glass? Where do electrons come from? Electrons EVERY one is more or less familiar with the fact that ordinary matter can be broken up into very small particles. Sugar, for instance, is most commonly seen in the granulated form, which parts are visible to the naked eye. Powdered sugar is another familiar form. It takes a very keen eye to detect the particles of sugar in this form. Sugar may still further be divided by dissolving it in water, say a teaspoonful of sugar to a glass of water. No trace of the dissolved sugar can be seen. Its presence can be detected by tasting the water which is sweet. In dissolving the sugar, it has been broken up into the smallest possible particles. No matter what method is employed, the sugar could not be divided further. Similarly, other materials can be divided and subdivided until there comes a time when no further division is possible. These smallest particles of matter are known as molecules and atoms. An atom is the smallest division of matter. An electron is to electricity what an atom is to matter. An electron, therefore, is the smallest part into which electricity may be divided. It is negative electricity. It has been shown beyond any possibility of doubt that electrons are present in all kinds of matter — in everything; metals, paper, wood, everything. In the usual state of matter, these electrons do not manifest themselves. But if a body has more than the usual number of electrons or less than the usual number, the body is said to be electrically charged; being charged negatively in the first case, and positively in the second case. As an electron is the smallest possible charge of negative electricity, a body is caused to have a negative charge by an excess of electrons and is caused to have a positive charge by a deficiency of electrons. From theoretical consideration, it was long suspected that such a thing as the electron existed. Their presence was detected by the use of tubes similar to X-ray tubes. Having detected them, scientists were quick to go about making measurements of them. After a lapse of some time, and as a result of very careful and brilliant work, the mass, electrical charge, and dimension of an electron became known. One very noteworthy experiment in measuring an elec tron was performed by an American, Prof. Millikan of Chicago. He introduced a minute drop of oil of about i-io,oooth inch in diameter in a chamber between two plates whose electrical charge was subject to control. The drop of oil was strongly illuminated and was viewed by a telescope. By controlling the potentials of the plates the oil drop could be made to fall or rise at will. The drop continually picked up and lost electrons. As it picked up an electron, it would move toward the positive plate (unlike charges attract); if it picked up two electrons it would move faster toward that plate. By carefully observing the action of the drop of oil, Millikan was able to determine very accurately the charge added to it by its picking up one electron. The electron is inconceivably small in mass, in size, and in the charge it carries. It would take more than a million million of them laid side by side to make an inch. Thus it is seen that it is too small ever to be made visible by any means. When an ampere of current is passing through a wire, more than six million million million electrons pass any given point in the wire each second. A detector tube has a plate current of about 20 milliamperes. As this is i-50th of an ampere, then the number of electrons passing from the filament to plate is about one hundred and twenty thousand million million per second. This number is inconceivably large. Millikan says that the number of electrons which pass every second through a common i6-candle power lamp is so large that it would take two and a half million people, twenty thousand years of twenty-four hour working days to count the number if they all counted at the rate of 120 per minute. It is seen from the above that a current of electricity is a flow of electrons. When man first commenced to study electricity he thought that there were two kinds, which he named positive and negative. As has been already noted this was an error, for there is only one kind and an excess or deficiency of this kind gives what was called negative and positive electricity. Soon man discovered that if a positively charged body and a negatively charged body were connected by a wire, electricity would flow along the wire. The direction of the flow of current was taken to be from positive to negative. This was also an error which has persisted to the present day. It is now known that nothing passes from the positive to the negative charge. On the contrary, the electrons pass from negative to positive and thus make the current. Ordinarily, however, we speak of the current as passing from positive to negative. The error is so deeply planted in all literature dealing with electricity and so many rules have been formulated upon it that it is too late to change it now. However, when one thinks about electrons, he must be aware of the fact