. The principles and practice of roentgenological technique . able tosupply a pressure of 200 volts at no loadthere is connected a copper circuit of negli-gible resistance, in which are two pieces ofGerman silver wire, one of 18 ohms resistanceand one of ohms resistance and the wind-ings of the generator have .1 ohms resistance,the amount of current the 200 volts pressureis able to force through the 18-|( resistance may be estimated by applyingOhms Law, E=IR where E is voltage, I isamperage and R is ohms resistance. Inthis case 200 = I X 20. Therefore I = the amperag
. The principles and practice of roentgenological technique . able tosupply a pressure of 200 volts at no loadthere is connected a copper circuit of negli-gible resistance, in which are two pieces ofGerman silver wire, one of 18 ohms resistanceand one of ohms resistance and the wind-ings of the generator have .1 ohms resistance,the amount of current the 200 volts pressureis able to force through the 18-|( resistance may be estimated by applyingOhms Law, E=IR where E is voltage, I isamperage and R is ohms resistance. Inthis case 200 = I X 20. Therefore I = the amperage in the circuit, the vol-tage lost in each of the resistances maybe determined by this same law. For ex-ample, since 10 amperes is flowing throughthe 18 ohm unit, then E= 10X18 =, ISO volts is lost or used up in thisunit; 10 amperes is flowing through ohm& 6 DE\^ELOPMENT OF ELECTRO-MOTIVE FORCE BY CHEMICAL ACTION then E:= lOX L9= 19 volts lost in the sec-ond unit and similarly 1 volt is lost in thegenerator. Thus, 180 + 19 + 1 = 200. i. \ __. f^esiroKe = Of Fig. I Ohms law is useful to determine how much-current a given voltage will force through agiven resistance, or how much voltage will beneeded to force the current through a givenresistance; or, given a voltage and knowingthe current, the amount of resistance in the•circuit may be ascertained and consequentlythe size of the wire needed to prevent toomuch voltage loss may be determined. Pozvcr {ivatt). The watt is the power orthe amount of energy developed by a currentof one ampere flowing under a pressure ofone volt. The product of amperes multipliedby volts equals watts as a symbol of kilo-watt equals 1,000 watts which is ap-proximately ly^ horse-power. One kilo-wattmaintained for one hour is called a kilo-watthour. The above rule may be expressed as fol-lows : ■ P = IXE (1) But I = E_R (see above) -(2) Therefore V=^X £-=- —^ R Electromotive force squared ■or Power in Watts;^ Resist
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
