Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . ch (preferably with a second hand). Note the level of theliquid on the burette scale before starting the test. Close the switch,noting the exact time. Allow the gas to be evolved till either thehydrogen limb of U tube is nearly full, or the liquid in the buretteapproaches the end of the scale. Bo not run above scale limit. Notethe time of opening the switch, also the height of the liquid in theburette. Prob. 7: The following data is recorded in Exp. 35. Find thestrength of current. L
Lessons in practical electricity; principles, experiments, and arithmetical problems, an elementary text-book . ch (preferably with a second hand). Note the level of theliquid on the burette scale before starting the test. Close the switch,noting the exact time. Allow the gas to be evolved till either thehydrogen limb of U tube is nearly full, or the liquid in the buretteapproaches the end of the scale. Bo not run above scale limit. Notethe time of opening the switch, also the height of the liquid in theburette. Prob. 7: The following data is recorded in Exp. 35. Find thestrength of current. Level in burette before test c. c. Level in burette after test c. c. Volume of gas evolved = — = c. c. Time of closing switch — 15. Time of opening switch — 15. Length of run = 5 minutes = 5 X 60 = 300 seconds. 26 2Total ga? generated per second = —^ = .0873 c. c. oOO One ampere in one second (one coulomb) generates .1733 cubic centimeters of gas per second, therefore Q = .5 ampere, V 26 2 or by Formula (7) C = ^ = m3 x m = .5 ampere. 100 PRACTICAL When more accurate calculations are desired the following formulais used to find the current strength : V X h X X 76 (273 +C°) X t v J V = volume of gas in c. = height of barometer in °= temperature of room, Centigrade,where test is made,t = time (in seconds) gas is evolved. Prob. 8: In an experiment the volumeof gas generated in a gas voltameter wasfound to be 20 cubic centimeters in 50seconds, its temperature (taken as the tem-perature of the room) was 20 degrees,Centigrade scale, the pressure of the atmos-phere was equal to 75 centimeters of mer-cury. What was the current strength ?Bv Formula (10) r 20 X 75 X 273 U —.1733 X76 (273 + 20) X 50 = find the volume of gas generated by aknown current : „ _ .1733xCx76(273 + C°)Xt n.,V — hX273 UiJ Prob. 9: What volume of gas would beproduced in a gas voltameter in 30 secondsby a s
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