Watts and Energy
Country: United States
Date: February 2009
The Watt rating of fluorescent Lamp is 40 Watt. Is it the
total energy consumption? How's about the ballast?
Energy is measured in joules. The watt rating is NOT the energy consumption.
A watt is a joule per second. This is the rate at which energy is flowing. If
the light is on one second, 40 Joules of energy are transferred. If it is on for
100 seconds, 4000 J of energy are transferred. Both examples transfer energy at
the rate of 40 Joules/second (40 watts). The 40 watt rating is for the bulb only.
Other components must be added in for the full energy transfer.
--Nathan A. Unterman
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Update: June 2012