LinuxQuestions.org Distribution of power in a microwave oven
 General This forum is for non-technical general discussion which can include both Linux and non-Linux topics. Have fun!

Notices

 02-18-2008, 01:27 PM #1 JoeyAdams Member   Registered: Jun 2006 Distribution: Kubuntu Hardy Posts: 94 Rep: Distribution of power in a microwave oven The microwave directions for a calzone I ate today say to cook only one at 50% power. I decided to cook two at a time with 100% power, and they tasted great. My question is: What is the mathematical relationship between the number of calzones in a microwave and the amount of cooking power one of the calzones receives? Is it an inverse relationship like this: P = k/n where P is cooking power, k is a constant based on time of cooking and microwave's wattage, and n is the number of calzones. Or is the P to n relationship a more interesting curve? For instance, if one were to put a very small drop of water into the microwave and cook it, would all 1200 watts focus onto that drop of water and make it instantly vaporize, or would most of the energy reflect back into the heating element? The answer to that question would be key to understanding if microwave heating is perfectly inverse or not.
 02-18-2008, 01:35 PM #2 Jeebizz Senior Member Contributing Member   Registered: May 2004 Distribution: Slackware14.2 64-Bit Desktop, Devuan 2.0 ASCII Toshiba Satellite Notebook Posts: 2,669 Rep: Shouldn't also the mass of the food in question be taken into consideration, and not just the number of calzones?? That also usually affects how it is cooked in the microwave.
 02-18-2008, 02:36 PM #3 michaelk Moderator   Registered: Aug 2002 Posts: 18,573 Rep: Typically the more mass the more cooking time required. Lowering the power setting when just heating a single calzone will allow it to heat more evenly and not burn the outsides first. Since no oven heats identically then there should be some additional factor. If all we are talking about is calzones then the total mass is just a function of the number. There will be microwave reflections based on the what type of food you are cooking and there will be reflections so not all power will be focused at a single spot.
 02-18-2008, 02:44 PM #4 pixellany LQ Veteran   Registered: Nov 2005 Location: Annapolis, MD Distribution: Arch/XFCE Posts: 17,802 Rep: I think the fundamental relationship is energy vs. water content (specifically the mass of water). A microwave works by agitating the water molecules ( at about 2.5GHz ). If you are just heating water, there is probably a pretty linear relationship between temperature rise and total energy (power X time). the "power" setting is really duty cycle, So the energy delivered is: E = W x P x t where: W = the total power output of the oven (eg ~ 1000watts) P = the "power" setting as a decimal (eg a setting of "5" is 50% or 0.5) t = cooking time To raise a cup of water by 100 deg F should take the same total energy, regardless of where P is set For food that is a mixture of ingredients, I suspect things are more complicated. For example, you would need to take into account the heat transport in the mixture. (The reason reduced power is used for thawing is to allow the energy to uniformly distribute in the material being heated) Another factor is the coupling efficiency. The microwave source sends the radio waves into the cavity, where they bounce around and set up patterns known as standing waves. These patterns will be influenced by how much material is in the cavity absorbing the waves. (All this is why the better ovens have a turntable) Why does bread get tough when microwaved? My guess is that the heat conductivity is poor and so there is local cooking where the water is.
02-19-2008, 04:59 PM   #5
Member

Registered: Jun 2006
Distribution: Kubuntu Hardy
Posts: 94

Original Poster
Rep:
Quote:
 Originally Posted by Jeebizz Shouldn't also the mass of the food in question be taken into consideration, and not just the number of calzones?? That also usually affects how it is cooked in the microwave.
Calzone is my unit of mass I'm asserting all calzones are equal in this analysis. Indeed, both mass of food and cookability (resonance of molecules to microwave radiation) must be taken into account.

Quote:
 Another factor is the coupling efficiency. The microwave source sends the radio waves into the cavity, where they bounce around and set up patterns known as standing waves. These patterns will be influenced by how much material is in the cavity absorbing the waves. (All this is why the better ovens have a turntable)
Hmm, I never thought about that benefit of a turn table

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is Off HTML code is Off Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post LXer Syndicated Linux News 0 04-26-2006 03:03 AM caa718 Linux From Scratch 3 03-19-2006 05:03 PM icic Linux - Newbie 1 07-13-2005 05:20 AM icyfire Linux - Software 4 06-24-2004 03:34 PM Capt_Caveman General 1 01-17-2004 05:46 PM

LinuxQuestions.org

All times are GMT -5. The time now is 05:46 PM.