Guide to the Practical Elements of Electrical Testing |
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Page 5
... in series by depressing the key shown in the figure. When inserted in the order
mentioned above, they reduce the sensitiveness of the instrument in direct
proportion, and the ohmio resistances between the outside terminals from an
original ...
... in series by depressing the key shown in the figure. When inserted in the order
mentioned above, they reduce the sensitiveness of the instrument in direct
proportion, and the ohmio resistances between the outside terminals from an
original ...
Page 37
... provided, as shown ; C is a contact slider with a knife-edge contact piece
mounted on a spring plunger, which normally maintains it out of contact with the
wire A B, but allows it to make contact with the latter at one point only when
depressed.
... provided, as shown ; C is a contact slider with a knife-edge contact piece
mounted on a spring plunger, which normally maintains it out of contact with the
wire A B, but allows it to make contact with the latter at one point only when
depressed.
Page 61
At its free extremity the spring is provided with an ebonite finger-piece, by means
of which it can be depressed out of contact with the second terminal on to an
insulating ebonite stud. To keys of this type illustrated above a revolving ebonite
...
At its free extremity the spring is provided with an ebonite finger-piece, by means
of which it can be depressed out of contact with the second terminal on to an
insulating ebonite stud. To keys of this type illustrated above a revolving ebonite
...
Page 62
The action of the key will be easily understood ; if one of the springs, A, for
example, be depressed, it is brought into connection with the ( — ) negative pole
of the battery, whilst the remaining 'spring, B, is in contact with the ( + ) positive
pole ...
The action of the key will be easily understood ; if one of the springs, A, for
example, be depressed, it is brought into connection with the ( — ) negative pole
of the battery, whilst the remaining 'spring, B, is in contact with the ( + ) positive
pole ...
Page 63
... pedestal mounted in the base. The springs A and B are provided with the usual
platinum-tipped contact studs on the under side of their free extremities, which C
Fig. 27. make contact when depressed by the finger-pieces with two similar. 63.
... pedestal mounted in the base. The springs A and B are provided with the usual
platinum-tipped contact studs on the under side of their free extremities, which C
Fig. 27. make contact when depressed by the finger-pieces with two similar. 63.
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Common terms and phrases
adjustable apparatus applied arms arranged balance base battery bridge Bros cable capacity cell charging circuit closed coil comparatively complete conducting conductor connected consequent consists constant constructed containing copper deflection depressed described determined difference direction discharge earth ebonite effect electrical employed equal extremity fault figure follows force galvanometer give glass illustrated indicated insulation known latter lead length lever magnetic manner means measurement mercury method mounted moving necessary needle noted obtained ohms ordinary passing period placed plugs pole position possible practical principle reading represented resistance respectively scale short shown shunt side similar simple slide solution spring standard standard cell suitable surface suspended switch taken taking temperature terminals tion tube turn unit usually vanometer varies voltage Wheatstone whilst wire zinc
Popular passages
Page 40 - It is convenient to arrange the mounting so that the cell may be immersed in a water bath up to the level of, say, the upper surface of the cork. Its temperature can then be determined more accurately than is possible when the cell is in air. " In using the cell, sudden variations of temperature should, as far as possible, be avoided.
Page 50 - As a unit of resistance, the international ohm, which is based upon the ohm equal to 10" units of resistance of the CGS system of electromagnetic units, and is represented by the resistance offered to an unvarying electric current by a column of mercury at the temperature of melting ice, 14.4521 grams in mass, of a constant cross-sectional area and of the length of 106.3 centimetres.
Page 40 - Then insert the cork and zinc rod, passing the glass tube through the hole prepared for it. Push the cork gently down until its lower surface is nearly in contact with the liquid. The air will thus be nearly all expelled, and the cell should be left in this condition for at least twenty-four hours before sealing, which should be done as follows.
Page 40 - Contact is made with the mercury by means of a platinum wire about No. 22 gauge. This is protected from contact with the other materials of the cell by being sealed into a glass tube. The ends of the wire project from the ends of the tube ; one end forms the terminal, the other end and a portion of the glass tube dip into the mercury.
Page 38 - ... carefully removing any loose pieces of the zinc. Just before making up the cell, dip the zinc into dilute sulphuric acid, wash with distilled water, and dry with a clean cloth or filter paper. 3. The Mercurous Sulphate.
Page 38 - CELL. Definition of the Cell. The cell consists of zinc or an amalgam of zinc with mercury and of mercury in a neutral saturated solution of zinc sulphate and mercurous sulphate in water, prepared with mercurous sulphate in excess. Preparation of the Materials. 1. The Mercury. — To secure purity it should be first treated with acid in the usual manner, and subsequently distilled in vacuo. 2. The Zinc. — Take a portion of a rod of pure redistilled zinc, solder to one end a piece...
Page 39 - Mix the washed mercurous sulphate with the zinc sulphate solution, adding sufficient crystals of zinc sulphate from the stock bottle to ensure saturation, and a small quantity of pure mercury. Shake these up well together to form a paste of the consistence of cream. Heat the paste, but not above a temperature of 30° C.
Page 40 - ... rod can pass tightly ; at the other side bore another hole for the glass tube which covers the platinum wire ; at the edge of the cork cut a nick through which the air can pass when the cork is pushed into the tube. Wash the cork thoroughly with warm water, and leave it to soak in water for some hours before use. Pass the zinc rod about 1 centimetre through the cork.
Page 39 - ... any free acid. The crystals should be dissolved with the aid of gentle heat, but the temperature to which the solution is raised should not exceed 30° C.
Page 20 - An example which deserves to be taken as a model by other authors. The subject Is treated In a manner which any intelligent man who is fit to be entrusted with charge of an engine should be able to understand.