. A manual of X-ray technic . hales, about 600 first noticedsome of the phenomena of electricity. The word elec-trics was first applied by Dr. Gilbert about the year1600 to certain substances like amber, sealingwax, etc., which become electrified by friction. Thephenomena of electricity are supposed to be due tosome stress or strain in the ether. Electricity may be either static or dynamic. Static electricity is electricity at rest; it is pro-duced by some form of friction or influencemachine. Dynamic electricity may be galvanic or faradic. Faradic electricity is a derived (induced)
. A manual of X-ray technic . hales, about 600 first noticedsome of the phenomena of electricity. The word elec-trics was first applied by Dr. Gilbert about the year1600 to certain substances like amber, sealingwax, etc., which become electrified by friction. Thephenomena of electricity are supposed to be due tosome stress or strain in the ether. Electricity may be either static or dynamic. Static electricity is electricity at rest; it is pro-duced by some form of friction or influencemachine. Dynamic electricity may be galvanic or faradic. Faradic electricity is a derived (induced) form ofelectricity, so named from Michael Faraday, in whichthere are rapid alternations of direction. Galvanic electricity is that produced by the gal- 2 A MANUAL OF X-RAY TECHNIC vanic cell, which, in its simplest form, consists of ajar of dilute sulphuric acid in which are dipped a plateof zinc and one of copper (Fig. 1). According to the theory of Arrhenius the affinityof the zinc for the acid radical SO4 starts a chemical. Fig. 1.—The galvanic cell. reaction which results in the determination of positiveions toward the copper and of negative ions towardthe zinc. In consequence of this ionic movement anelectrical current is produced from the zinc to thecopper through the liquid, and outside of the cellfrom the copper to the zinc through a connectingwire. ELECTRICITY AND MAGNETISM 3 Polarization of a galvanic cell takes place by thecollection of bubbles of hydrogen gas on the copperplate and interferes with or stops the action of thecell. Various devices have been used to prevent this. Types of Cells.—There are many different typesof cells, but only two will be described here. The Daniell cell consists of a zinc plate immersedin dilute sulphuric acid contained in a porous vessel,outside of which is a perforated copper plate sur-rounded by a solution of copper sulphate. Thehydrogen is taken up by the sulphate before it reachesthe copper plate. This cell is very constant be
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbones, bookyear1917
