. Electrical news and engineering . mum, and thendecreases again to nothing. Turning to diagram No. i,we will suppose ring C to be one of the coils of analternating dynamo. In the position where C is perpen-dicular to the lines of force N S, any very slight revolv-ing of A will not vary the amount of them contained byC much ; in fact in this position a slight revolving willreally generate no E. M. F. at all, but as A is revolved(counter clockwise) ring C will hold less and less linesof force until it reaches the position in diagram 2, whenthe rate at which C is decreasing is greatest, and as t
. Electrical news and engineering . mum, and thendecreases again to nothing. Turning to diagram No. i,we will suppose ring C to be one of the coils of analternating dynamo. In the position where C is perpen-dicular to the lines of force N S, any very slight revolv-ing of A will not vary the amount of them contained byC much ; in fact in this position a slight revolving willreally generate no E. M. F. at all, but as A is revolved(counter clockwise) ring C will hold less and less linesof force until it reaches the position in diagram 2, whenthe rate at which C is decreasing is greatest, and as theE. M. F. generated depends on the rate of variation,the highest E. M. F. generated in C will be when it ispassing through the position in diagram 2, and a pro-portionate E. M. F. will be generated in C at any inter-mediate position. So that the E. M. F. will grow dur-ing a quarter revolution from o to a maximum. WhenC has been revolved through a half turn, conditions willbe as they were in diagram No. i, and at this point no J^J^. lui^ A<y £Uir E. M. F. will be generated in C, it having decreasedfrom the position of maximum E. M. F. in diagram C be revolved through and then quarter turn, theneverything will be the same as in diagram No. 2, andthe E. M. F. will again be at a maximum, except thatthe direction of the E. M. F. has reversed, and insteadof being from right to left is now from left to right ; or,if we call the first direction positive we can call the newone negative. From the third quarter revolution to thefourth brings C back to the first position. All thesechanges can be put into a diagram form as in No. 4,where the curved line shows how the E. M. F. in thering varies between a positive and a negative will be understood that whereas the direction of theE. M. F. is from right to left in the upper part of thediagram, it becomes from left to right in the lower ; thestrength of the E. M. F. at any point in the revolutionbeing indicated by the heigh
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