[Electric engineering.] . attmeter in acircuit not to get the current and pressure terminals con-fused, because if the current terminals were connectedacross the line, a short circuit would result, and the instru-ment would, in all probability, be destroyed. There is gen-erally no excuse for making such a mistake as this, becausethe terminals are entirely different in appearance; never-theless, it has been known to occur. If the fine-wire coil isconnected in series in the circuit, no damage will result,but scarcely any current will flow onaccount of the high resistance so in-troduced. 95. If a
[Electric engineering.] . attmeter in acircuit not to get the current and pressure terminals con-fused, because if the current terminals were connectedacross the line, a short circuit would result, and the instru-ment would, in all probability, be destroyed. There is gen-erally no excuse for making such a mistake as this, becausethe terminals are entirely different in appearance; never-theless, it has been known to occur. If the fine-wire coil isconnected in series in the circuit, no damage will result,but scarcely any current will flow onaccount of the high resistance so in-troduced. 95. If an indicating wattmeterwere connected to a motor as shownin Fig. 37, it would indicate the powersupplied, and its readings would varyas the load on the motor power is sold to customers froma central station, it is generally moreimportant to know the total amountof work done during a given intervalof time than the power that themotor or other device is taking at anyfig. 37. particular instant. For example, the. § 14 ELECTRIC TRANSMISSION. 83 company supplying power wishes to know just how muchwork has been done during, say, 1 month, so that the billmay be rendered accordingly. If we do work at the rate of1 watt, i. e., 1 joule per second, and keep this up for an hour,we do a certain definite amount of work. This quantity ofwork is known as the watt-hour. 1 joule is equivalent foot-pound, and .7373 foot-pound per second is 1 , then, we work at the rate of 1 watt and keep it up for1 hour, or 60 X 60 seconds, at the end of the hour we willhave done .7373 X 60 X 60 = 2, foot-pounds of order to obtain the total amount of work expended onany device, we must use some instrument that will give usthe product of the average rate at which work has beendone by the time during which it was done. Such aninstrument is known as a recording wattmeter, or watt-hour meter. The latter name is preferable, because thereadings of these instruments do not give
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