How Do Microwave Ovens Really Heat Food?

[SlowBrownFox]

Hello,

I am conducting an independent study on whether there are any adverse effects to human health from eating food heated with a microwave oven.

Upon researching how microwave ovens work, I am finding conflicting views on how the food is heated.

I frequently find statements that say microwaves heat by vibrating molecules, which results in friction between those and other molecules, and the friction creates the heat.

“The water molecules in the food vibrate violently at extremely high frequencies – like millions of times per second – creating molecular friction, which heats up the food.”
–mercola.com


“Microwaves agitate the molecules to move faster and faster. This movement causes friction which denatures the original make-up of the substance.”
–usahitman.com

“Microwaves cause water molecules in the outer layers of food to vibrate. The vibration causes friction between the molecules, which produces heat. That heat then causes neighboring molecules to vibrate, which in turn heat up and so on.”
–Facebook user Bob Drummond via howstuffworks.com

“The oven's electromagnetic field oscillates as it passes through the water molecules in the food, changing the polarity of the field and causing the dipole/water molecules to flip themselves in order to be aligned with the new polarity." Heat is created by the resulting friction of the water molecules reversing direction millions of times a second.”
–Tom Fitzgerald via psu.edu



Otherwise I find statements that say microwaves heat by dielectric heating. It is my understanding that these are completely different. That dielectric heating has nothing to do with how friction creates heat. Am I correct? Which is the actual way microwave ovens heat food?

[theborg]

SlowBrownFox,

Thank you for your question. Your quoted text is the description of how a microwave heats food. Dielectric heating is the technical term for the effect described. They are one and the same.

[SlowBrownFox]

SlowBrownFox,

Thank you for your question. Your quoted text is the description of how a microwave heats food. Dielectric heating is the technical term for the effect described. They are one and the same.

Thank you.

I thought that the constant rotation of the polar molecules increases kinetic energy because their motion is increased, and so the temperature of the food in increased. But it is friction that causes an increase in temperature?

[deleted-2131]

Hi SlowBrownFox,

Temperature is a measure of the average kinetic energy of a substance. So, the increase in temperature comes from the fact that the molecules are moving more rapidly, which increases their kinetic energy.