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Stubby

Nice experiment! Thanks.

wrote:
This morning I put two $20 Kill-a-Watt meters on two power strips with
a 100 W bulb screwed into one plug socket 80 cm from a "100 W equivalent"
23 W 10,000-hour Commercial Electric compact fluorescent with a 9-year
guarantee ($8.97 for 4 from Home Depot) and compared the outputs with
a Bunsen grease-spot photometer (a drop of oil on a piece of white paper :-)

Robert Bunsen (1811-1899) also invented the Bunsen burner. He was known as
an inept experimentalist with radical theories who isolated a foul-smelling
compound which he named cacodyl oxide and a whole series of related compounds
which turned out to be highly explosive. At one point, Bunsen accidentally
blew up his lab and was laid up in bed for a long time.

The grease spot disappeared (indicating equal illumination on both sides) when
the paper was 42.4 cm from the incandescent bulb, so it had (42.4/(80-42.4))^2
= 1.27 times the CF light output. After a minute or so, the 100 watt bulb
consumption dropped from 100 to 99 watts and the CF rose from 22 to 24, so
the CF was 99/(1.27x24) = 3.24 times more efficient, with 3.24 times more
lumens per watt.

After warmup, a "150 W equivalent" 42 W CF ($5.97 from Home Depot) used
35 watts and made the spot disappear 36.2 cm from the 100 W bulb when
it drew 98 watts, so it was (36.2/(80-36.2))^2 = 0.683 times brighter
than the CF, which was 98/(0.683x35) = 4.10 times more efficient.

Nick