Electric bell construction; a treatise on the construction of electric bells, indicators, and similar apparatus

9781235944956: Electric bell construction; a treatise on the construction of electric bells, indicators, and similar apparatus

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1914 Excerpt: ...the magnet so as to better enclose the armature. "When the currents of electricity are induced in the armature, the armature becomes for the time an electro-magnet, and the currents in the armature are always in such a direction as to oppose the motion. This will become apparent on slowly turning the armature of the generator, when it will be found to move in a jerky manner if the circuit is closed, and comparatively freely if the circuit is open. As the direction of the current is reversed at each half revolution of the armature, we see that the current given out by the generator is an alternating one, the rapidity of the alternations depending on the speed at which the armature is rotated. This alternating current is not adapted for working the ordinary form of electric bells, as these are designed to work with a current that flows always in one direction, such as is given out by a battery, so a different form of bell is used. The first forms of the magneto bell were similar to the Siemens polarised relay, the armature being a permanent magnet, and working between two electro-magnets. It had many faults, however, the chief of which were its sluggish action and the liability of the armature to lose its magnetism. The great improvement of the modern magneto bell over the old form consists in the substitution for the polarised steel armature of a soft iron one inductively magnetised by a permanent magnet placed in close proximity to it. Figs. 128 and 129 show a diagrammatic view of the modern magneto bell, Fig. 129 being a side view of Fig. 128, with the right hand gong removed. The bell, it will be seen, consists of the electro-magnet e, opposite the poles of which is the armature a. This armature is pivoted at the centre, and from the centre also spri...

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