[Electric engineering.] . ed, it will be found that different values for the can-dlepower will be obtained, depending on the position of thelamp and the shape of the filament. For example, in Fig. 15the brightness of the lamp in the different horizontaldirections i, 2, 3, 4-, etc., would not be the same. The can-dlepower given out in the different horizontal directionsalong any line, such as those shown in Fig. 15, is known asthe horizontal candlepower for that position. The meanor average horizontal candlepower is the average value ofthese different readings. This mean horizontal candlepoweri
[Electric engineering.] . ed, it will be found that different values for the can-dlepower will be obtained, depending on the position of thelamp and the shape of the filament. For example, in Fig. 15the brightness of the lamp in the different horizontaldirections i, 2, 3, 4-, etc., would not be the same. The can-dlepower given out in the different horizontal directionsalong any line, such as those shown in Fig. 15, is known asthe horizontal candlepower for that position. The meanor average horizontal candlepower is the average value ofthese different readings. This mean horizontal candlepoweris sometimes obtained by taking the reading from the lampwhile it is rapidly revolved about its vertical axis. The 16 ELECTRIC LIGHTING. 23 photometers just described are arranged so that the lampmay be revolved at the rate of about 180 revolutions perminute, thus giving the average, or mean, horizontal candle-power. The horizontal candlepower does not vary greatlyin different directions with lamps as now constructed. This. Fig. 15. is shown by the irregular curve (Fig. 15). The distance ofthe points on this curve from the center represents the can-dlepower in the direction of the radius from that point, aridif the candlepower were the same in all directions, this curvewould become a circle. 29. Vertical Distribution.—Fig. 16 shows the readingsfor the candlepower obtained in a vertical plane with afilament in the positionshown. It will be no-ticed that, viewed fromposition 1, the candle-power is practically zero,because the light isalmost completely cutoff by the base of thelamp. At points 2 andJf it is a maximum, be-cause viewed from thesepoints the maximumamount of the filament is fig. 16. seen. At point 3 the candlepower again drops off, becausehere the filament is seen end on. The curve of horizontaldistribution gives an idea as to how the lamp throws light
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