File:Core-less induction coils in telephone service (1907) (14569314848).jpg

Identifier: corelessinductio00smit (find matches)
Title: Core-less induction coils in telephone service
Year: 1907 (1900s)
Authors: Smith, Claude E Stewart, Walter M
Subjects: Induction coils Telephone Telephone systems Theses
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Contributing Library: University of Illinois Urbana-Champaign
Digitizing Sponsor: University of Illinois Urbana-Champaign

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resemble moreperfectly the tone and pitch of the human voice, hut was lackingthat intensity of soimd of the standard coil. This lack of inten-sity was perhaps due to the fact that v;e had no iron core. We trieto rig up a core made of strips of sheet iron wound about the twocoils and overlaping each other, but the result was not satisfact-ory. The flux though that sort of a core seemed to be non-contin-Vious. We tried to bend a gas pipe so as to fit betv/een the two coibut we were unable to get a piece of pipe that could be made to fiin well and give any result. As an experiment we cut two pieces ofsheet iron larger than the test coil, and placed one above and onebelow the coil. This arrangment reduced the sound about sixty per-cent, due to the fact that the flux set up eddy currents in theiron, these eddy currents set up a flux which reacted upon the primary flUA, thus decreasing the total fluA cut by the secondaryturns, and hence deminishing the sound transmited. We nov; confined lb
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5 our work to tests on the coil without any kind of a core. The secondary of the test coil was now p^raduall y lifted above,vertically away from the primary, every monientary position beingparalell to the position of the plane of the pri-nary. ( see dia-gram 3 of coila ). At a distance of one foot, sound was very audi-ble, with a slight deni.xishing of intensity. Beyond this distance,still raising the socoiidary, sound grew fainter and fainter untillat a distance of two feet, it was just possible to make out Y/hatwas said. It seems then , that the flux due to the primary coil isstill very much concentrated even at a distance of one foot, andthat it diverges rapidxy beyo.id that distance. The secondary was now moved thro\igh angles of thirty, sixty,ninty, etc, up to one-hundred an,d-eighty degrees, with reference tothe primary. At ninty degrees the edge of the secondary was restingin the plane ( center of ) of the primary ar. shown in diagram 4, ofcoils. As the angles between the coils

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