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Rants, Raves, Interesting Science & Awful Puns
December 9, 1998

Telling It Like It's Not

Confused by Numbers? Try Magic Instead.

The starting point with any science is understanding the elementary definitions and units. At one time this was covered in the first classes devoted to a subject. Nowadays, it seems, teachers, writers, variously acknowledged experts, and even textbooks can get by without bothering to learn the fundamentals of the issues they pose as authorities on. Howard Hayden, in the November 1998 issue of his newsletter The Energy Advocate, lists some examples from a collection of sources relating to electrical power generation.

(Mini-tutorial: Energy is the capacity to do work, which is defined as a force acting over a given distance. Thus, a five-pound weight at the top of a 100-foot-high building has the potential energy to perform 500 foot-pounds of work in descending to the ground. The energy is imparted by raising the brick up from ground level, and is the same whether the brick was carried up via the stairs in minutes or whisked up in seconds by an elevator. The elevator, however, operates at higher power. Power is the rate of doing work, measured as energy/time, in the above units, foot-pounds per second. Or putting it another way, energy equals power multiplied by time.

In electrical units energy is measured in joules, kilojoules, etc., and power is given by joules per second, which defines the watt. Hence, energy in joules equals watts multiplied by seconds, or watt-seconds. Energy is what you’re billed for by the utility company. For convenience, however, the unit generally employed is the kilowatt-hour, which is still power multiplied by time. The watt, or kilowatt, gives the rate at which energy is used.

If the above is new it may require rereading. But it isn’t really that complicated. Now compare the inanities highlighted in the examples below, taken from wisdoms dispensed for the guidance and greater edification of school- children and the general public.)

"The drain from such devices in U.S. homes alone adds up to 5 billion watts per year . . ."

Business Week, October 5, 1998, p.115

(This—power divided by time—could mean something only if the number of devices in homes were changing, for example if increasing sales of light bulbs were adding to the load at some number of watts extra every year.)

"What is a kilowatt? A 100 watt light bulb uses 100 watts per hour of use. It will use 1,000 watts if burned for 10 hours. A kilowatt is 1,000 watts."

— Chapter Three, "Why is it Happening?" of book for Grade 6, (Marco Press, 1997) http://www.opnated.org/6u3.htm

"The standard unit of measure of electrical use is the kilowatt-hour (divide the wattage by 1000 to convert to kWh).

— APS Online: Power Posse, Fourth Grade Activity

"A 100-watt bulb uses 100 watts of electricity in an hour. In 10 hours this bulb would use 1000 watts of electricity. One, 100-watt bulb burning for 10 hours would use 1,000 watts, or one kilowatt of electricity . . ."

— Energy Conservation Enhancement Project, Louisiana

(A kilowatt doesn’t measure an amount of electricity. A kilowatt-hour does.)

"How much are customers saving now? More than 200 million kilowatts per year . . ."

— Eugene Water and Electric, http://eweb.org/about/history/conservation.html

"Examples of the new energy-minded refrigerators include Kenmore’s model 95529 which requires 561 kilowatts per year . . ."

— http://www.brown.edu/Departments/Brown_Is_Green/greenarch/Watson.html

"Electrical Trivia: It takes _________ gallons of oil to make 1,000kW/hr of electricity . . ."

— Electronic Educational Devices Inc., Denver. http://www.til.org/~eed/trivia.html

Maybe we should think about replacing all quantitative work in science with spells and mantras. Numbers are so confusing. And when you want to change reality, they just get in the way.

 
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