. An elementary book on electricity and magnetism and their applications. Fig. 332.—Vertical distribution for a lamp when fitted with a shade andwithout a shade. Note. — A one-candle-power lamp placed in the center of a sphereof one foot radius shines on (47r) square feet of surface. Thelight which shines on one square foot at a distance of one foot from alamp of one mean spherical candle power and at right angles to therays is called a lumen. Hence in general Lumens = Xmean spherical candle power. 8. If an ordinary lamp is rated as 4 watts per mean spherical candlepower, calculate
. An elementary book on electricity and magnetism and their applications. Fig. 332.—Vertical distribution for a lamp when fitted with a shade andwithout a shade. Note. — A one-candle-power lamp placed in the center of a sphereof one foot radius shines on (47r) square feet of surface. Thelight which shines on one square foot at a distance of one foot from alamp of one mean spherical candle power and at right angles to therays is called a lumen. Hence in general Lumens = Xmean spherical candle power. 8. If an ordinary lamp is rated as 4 watts per mean spherical candlepower, calculate the efficiency in lumens per watt. 9. Compute the efficiency (lumens per watt) of a gas-filled tungstenlamp rated at one half watt per mean spherical candle power. 10. A parkway 2 miles long is to be lighted by seriesincandescent lamps 175 feet apart. The voltage across each lampis 55 volts and the line wire is No. 7. If an extra mile of wire isneeded to complete the circuit through all the lamps, compute (a) thevolts needed when all the lamps are burni
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmagnetism, bookyear19
