. Revised and enlarged ed. of the science of railways . lectro-motiveforce) and the current. An exact analogue isfound in a force pump where the power dependsupon the pressure and the quantity of waterpumped, and the horse-power is found by multi-plying the pounds pressure per square inch bythe gallons per minute and dividing by seventeenhundred and fourteen. The electric horse-powerdelivered by a dynamo is found by multiplyingthe pressure in volts by the current in amperes(giving the watts) and dividing by seven hundred and forty-six. The outputin kilowatts is found bydividing the number ofwa
. Revised and enlarged ed. of the science of railways . lectro-motiveforce) and the current. An exact analogue isfound in a force pump where the power dependsupon the pressure and the quantity of waterpumped, and the horse-power is found by multi-plying the pounds pressure per square inch bythe gallons per minute and dividing by seventeenhundred and fourteen. The electric horse-powerdelivered by a dynamo is found by multiplyingthe pressure in volts by the current in amperes(giving the watts) and dividing by seven hundred and forty-six. The outputin kilowatts is found bydividing the number ofwatts by one power delivered to a^motor is similarly foundby multiplying theelectro-motive force bythe amperes. In this case,however, the current flowsagainst the pressure andthe power is delivered to the machine instead ofby it. A small current at high pressure willdeliver the same power as a large current at alow pressure. Five amperes at one thousandvolts is equivalent in power to ten amperesat five hundred volts, or fifty amperes at one. Winding a Railway GeneratorArmature. ELECTRICITY AS A MOTIVE POWER. 405 hundred volts, as the product is in each case fivethousand watts, or six and two-thirds horse-power. The power which appears as heat ina wire is similarly found by multiplying theamperes ])y tlie electro-motive force measuredbetween the ends of the wire. The power isequal also to the square of the number ofamperes multiplied by the ohms resistance, or, Watts —amperes x volts = amperes^ x olims-^C E -= C^ R. If twenty amperes flow through two miles ofNo. 3 B. & S. copper wire (two ohms) the Watts -^ C^ R = 400 x 2 ^ 800 - horse-power. ELECTRIC MACHINES. How Current is Produced in the Dynamo.—Tliereisa reciprocal relation between electricity and mag-netism. On the one hand, a current of electricitypassed around an iron core will make a magnet ofthe iron; on the other hand, if under proper con-ditions a wire be moved in a magnetic field ornear a magnet,
Size: 1630px × 1533px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1800, bookidsciencerailw, bookyear1800
