# The Microwave Equation

The instructions for my microwave tell me how retentive to reheat one serve of this or that. But sometimes I want to reheat two or more servings at the same time. To reheat “ ten ” issue of servings, should I set the timer for “ x ” times the phone number of minutes for a single serve ? Forgive me, but before I answer your question I must dispose of two positron emission tomography peeves. In algebra, “ ten ” stands for an unknown quantity. It is a issue. It therefore does not need to be followed by the give voice “ total. ” For an nameless number of servings, we should simply say “ x servings. ” If, for model, we wanted to talk about two servings ( i.e., x=2 ), we would n’t say “ two number of servings, ” would we ? Will everybody within the legal of my penitentiary please spread this password to all those who are going around these days saying and writing “ ten number of ” this or that ? Thank you. besides, what we put our food into is a microwave oven, not a microwave. A microwave, if you ‘ll pardon the techspeak, is a photon of electromagnetic radiation. I ‘m quite resigned to losing this battle, however, being mindful of how the original “ trunk compartment ” of an automobile became merely “ the torso. ” But “ baseball glove compartment ” has for some reason survived.

nowadays about heating things in your microwave. ( If you ca n’t lick ’em. .. ) To heat two servings of something, it takes less than doubly the meter required to heat one. much less. here ‘s how the arithmetical works out. First of all, the microwave generator, called a magnetron, does n’t know or care what ‘s inside the oven. It puts out a constant level of microwave baron, no count what. When you set the “ power ” for 50 percentage, for exemplar, the magnetron cycles on and off, so that it is on at full baron for half the time. So the “ power ” fructify does n’t affect our problem. But different foods absorb microwaves to different extents. Let ‘s say for the sake of argumentation that one of your servings absorbs — and turns into heat — 40 percentage of the microwaves that hit it. If that serve is alone in the oven, 60 percentage of the magnetron ‘s microwave output is not being absorbed. Let ‘s now imagine a moment, identical helping in the oven along with the first. It will absorb its own 40 percentage of the microwaves available to it, namely, 40 percentage of the 60 percentage that are not being absorbed by the foremost serve, or 24 percentage of the end product of the magnetron. The sum amount of microwave world power being absorbed by the two servings is then 40 percentage by the first service plus 24 percentage by the second serve, or a entire of 64 percentage of the magnetron ‘s output, rather of the expect 80 percentage ( 2 adam 40 ). To bring them both up to the desire temperature, then, the heat time must be lengthened by the component 80/64. so if a lone serving would require 10 minutes, then the two together would require 10 x 80/64 or 12.5 minutes. That ‘s a draw less than twice the time. ( The position is n’t in truth that simple, because the second serve perturbs the energy concentration of the first one and vice versa. But you credibly feel that this “ simplify ” explanation is complicated enough. ) I tested these ideas with my own “ ache ” microwave oven, which has preprogrammed cycles for respective common heat and cooking chores. For “ Heating a beverage, ” for example, the oven foremost wants me to press a button to tell it how many cups of liquid I want to heat. It then begins its preprogrammed heat cycle for that amount. here ‘s how long the cycles lasted : for 1/2 cup, 30 seconds ; for 1 cup, 50 seconds ; for 1 1/2 cups, 70 seconds ; for 2 cups, 90 seconds. You can see that the first 1/2 cup required 30 seconds, but that each extra 1/2 cup requires merely 20 extra seconds.

Another model : For “ Baked Potatoes ” ( they ‘re not being baked, of naturally, but I ‘ll let that one survive ), the oven cooks one potato for 4 minutes, 30 seconds ; two potatoes for 7 minutes, 40 seconds ; three potatoes for 10 minutes, 50 seconds ; and four potatoes for 14 minutes. That ‘s 4 1/2 minutes for one potato plus an extra 3 minutes, 10 seconds for each extra one. Putting it another manner, two potatoes take only 1.7 times vitamin a long as a single potato ; three potatoes take entirely 2.4 times as farseeing ; and four potatoes take entirely 3.1 times as long. Lacking a “ fresh ” oven, all you can do is guess. For two servings, your first think should be about 1 1/2 times the time required for a single serve. Bromate update In a holocene column, I said that the potassium bromate used in bleach and conditioning flour turns into harmless potassium bromide. That ‘s true, and in the about 100 years that flour has been bromated, no one had been able to detect any remainder bromate in adust goods that used bromated flour. But chemists now have such sensitive detection methods that very low levels of residual bromate can be detected. Because senior high school levels of bromate have been found to cause cancers in rats, the U.S. Food and Drug Administration has asked bakers to stop using it and find a utility. Canada and the United Kingdom have banned the chemical altogether. Labelingo : The rag that came with my wife ‘s newly kitchen proscenium says, “ Washing Instructions : Before washing, turn garment wrong-side-out. ” now please mental picture a kitchen apron and tell me how to turn it inside out.

( Have you noticed any silly things on food labels ? Send your Labelingo contributions, along with your name and town, to Food 101, Food Section, The Washington Post, 1150 fifteenth St. NW, Washington, D.C. 20071 or to the e-mail savoir-faire below. ) Robert L. Wolke ( www.professorscience.com ) is professor emeritus of chemistry at the University of Pittsburgh and the generator, most recently, of “ What Einstein Told His Barber : More scientific Answers to Everyday Questions ” ( Dell Publications, \$ 12.95 ). His future ledger, “ What Einstein Told His cook, ” is to be published by W.W. Norton next spring. Send your kitchen questions to wolke @ pitt.edu.