An elementary book on electricity and magnetism and their applications . both be drawn on the same horizontal base line. Figure 217shows an and also a curve of current in phase. It willbe noticed that the current and voltage are both at zero at the same instant, both passthrough their values at the same in- 360° w_^ stant, and in fact keep instep throughout theirentire cycles. This is thecondition of an alternat-ing-current circuit whichcontains resistance shall see that in alternating-current circuits we very oftenhave to consider other factors besides resistanc
An elementary book on electricity and magnetism and their applications . both be drawn on the same horizontal base line. Figure 217shows an and also a curve of current in phase. It willbe noticed that the current and voltage are both at zero at the same instant, both passthrough their values at the same in- 360° w_^ stant, and in fact keep instep throughout theirentire cycles. This is thecondition of an alternat-ing-current circuit whichcontains resistance shall see that in alternating-current circuits we very oftenhave to consider other factors besides resistance, such as induc-tance and capacity, which may cause the current to lag be-hind the voltage (Fig. y~P\ ^voltage218) or even to leadthe voltage (Fig. 219).The discussion of thecauses and effects oflagging and leading cur-rents will be the subject Of the next chapter. Fig. 219. — Current leading by 30°. Fig. 218. — Current lagging 50° behind 316 ELECTRICITY AND MAGNETISM 216. Ohms Law in noninductive a-c. circuits. Sometimesthere is doubt about how to use Ohms Law (section 30) in ; hence it will perhaps be well to recall again that thislaw states the relation of voltage, current, and resistance only,and always holds true as far as the relative values of thesealone are concerned. It will be seen that this law does not dealwith inductance or capacity. Therefore, when we are dealingwith resistance alone, we may be sure that the voltage neededto drive a certain current through a certain resistance is alwaysthe product of the current times the resistance, whether the voltageis direct or alternating. Problems 1. How many volts are needed to force 25 amperes alternatingcurrent through 8 ohms resistance? 2. Compute the number of watts consumed in the resistance ofproblem 1. 3. How much direct current would be required to cause the sameheating effect as the alternating current in problem 2 ? 4. What would be the maximu
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
