Guide to the Practical Elements of Electrical Testing |
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Page 1
... figure , it lies in a plane with the coil . If , however , an electric current be passed round the coil a b in either direction , the needle , N S , following a well - known law , tends to set itself at right angles to the plane of the ...
... figure , it lies in a plane with the coil . If , however , an electric current be passed round the coil a b in either direction , the needle , N S , following a well - known law , tends to set itself at right angles to the plane of the ...
Page 3
... figure , which indicates the movements of N S consequent upon the passage of a current , upon an engraved dial plate mounted behind a protecting glass front , in one of the sides of the case . Such an instrument as that described above ...
... figure , which indicates the movements of N S consequent upon the passage of a current , upon an engraved dial plate mounted behind a protecting glass front , in one of the sides of the case . Such an instrument as that described above ...
Page 5
... figure . When inserted in the order mentioned above , they reduce the sensitive- ness of the instrument in direct proportion , and the ohmic resistances between the outside terminals from an original total of 320 ohms to 32 , 16 , 8 , 4 ...
... figure . When inserted in the order mentioned above , they reduce the sensitive- ness of the instrument in direct proportion , and the ohmic resistances between the outside terminals from an original total of 320 ohms to 32 , 16 , 8 , 4 ...
Page 13
... Figure of Merit " in their list is reckoned in megohms , ie . , the number of megohms through which an E.M.F. of one volt at the terminals of the instrument will produce a deflection of one scale division ( 1-40th inch ) , and the ...
... Figure of Merit " in their list is reckoned in megohms , ie . , the number of megohms through which an E.M.F. of one volt at the terminals of the instrument will produce a deflection of one scale division ( 1-40th inch ) , and the ...
Page 16
... figure of merit , one volt through one megohm gives a deflection of 10 millimetres , using the 500 turn coil at a distance of two metres from the screen . When required , the . instrument can be made more portable by means of a 16.
... figure of merit , one volt through one megohm gives a deflection of 10 millimetres , using the 500 turn coil at a distance of two metres from the screen . When required , the . instrument can be made more portable by means of a 16.
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Common terms and phrases
adjustable arm alternating current ammeter ampère apparatus cable under test calibration capacity charging circuit key Clark Cell Co-eff coil conductor connected consists constant constructed copper D'Arsonval D'Arsonval Galvanometer Daniell cell deflection method deflection results depressed described discharge disconnected drum earth ebonite electrode electromotive force Elliott Bros extremity fault galvano glass high resistance immersed indicated in Fig instrument insulation resistance known latter leakage length lever localisation loop low resistance magnetic megohms mercurous sulphate mercury meter metre bridge millimetre mounted Nalder Bros nected needle noted Ohm's law ohms ordinary platinum plugs pole practical reading reflecting galvanometer represented in Fig resistance measurement respectively scale short circuit shown shunt sistance slide wire slider standard cell standard resistance suitable surface suspended switch temperature terminals testing battery tion total resistance tube usually vanometer voltage voltmeter volts Wheatstone bridge whilst zero zinc sulphate
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.