An elementary book on electricity and magnetism and their applications . ion,we have to use a commu-tator. To understand howthis works let us study avery simple case. If theends of the loop in section140 are connected with asplit ring, as shown in figure132, we may set the brushesB-\- and B— on oppositesides of the ring so thateach brush will connect first with one end of the loop and thenwith the other. By properly adjusting the brushes so thatthey shift sections on the commutator just when the currentreverses in the loop (that is, when the loop is in a verticalposition), we may get the curre
An elementary book on electricity and magnetism and their applications . ion,we have to use a commu-tator. To understand howthis works let us study avery simple case. If theends of the loop in section140 are connected with asplit ring, as shown in figure132, we may set the brushesB-\- and B— on oppositesides of the ring so thateach brush will connect first with one end of the loop and thenwith the other. By properly adjusting the brushes so thatthey shift sections on the commutator just when the currentreverses in the loop (that is, when the loop is in a verticalposition), we may get the current to flow out only at onebrush B + , and in only at the other brush B —. The direc-tion of the current in the external circuit is always the same,even though the current in the loop itself reverses twice inevery revolution. The voltage delivered by such a machine can be representedby the curve in figure 133. Although it is always flowing inthe same direction, it is pulsating. This is easy to understandafter a little consideration. When the coil stands up and down. Fig. 132. Split-ring commutation. 202 ELECTRICITY AND MAGNETISM +30«+20£ + 102 0 2- -30 ^ ?vj <^\ / \ / \ / / 1. \£ 1 FO ::7 N OF LC c? IN DEGREES Fig. 133. — Pulsating delivered by loop fittedwith commutator. between the pole pieces as in figure 132, it is in such a positionthat when it is revolved a small amount the conductors move practically parallelto the lines of forceand no lines arecut. When the coilis in continuousrevolution, no volt-age is induced atthe instant that itis in this position,which corresponds with the points 0°, 180°, and 360° on thecurve in figure 133. When the coil stands as shown in figure 134, it is in such aposition that the conductors cut squarely across the lines offorce as they move, and the largest possible number of lines offorce are cut for a given amount of motion. The position ofthe coil shown inthe figure andthe position 180°therefrom corre-spond with thepoi
Size: 2018px × 1238px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
