You've probably noticed that your microwave is heating up unevenly. It's a frustrating little thing that makes a difference in your meal. There's an easy way to find out where the hot spots are exactly. Once you know where the highest concentration is, you can position your dish for smoother cooking.
Finding the hotspots is a lot of fun, even if you do not care how uneven your food cooks. First put a plate covered with marshmallows in your microwave. To make this extra fun, swap the regular marshmallows and place peeps on the plate instead.
Set the microwave to high for 50 seconds and look through the microwave window. The marshmallows that inflate first are in a hot spot.
The science behind it
To heat heat, electromagnetic waves are transmitted from a vacuum tube, called a magnetron, to the top of the device. These microwaves cause the water molecules in the food to vibrate, and the friction generated by the vibration generates heat.
However, the microwaves are not emitted in a uniform pattern that envelops the entire shell. There are high and low electric field strengths of microwaves. The low electric field strength causes cooler points than the higher intensity points. The hot spots are in the areas of higher intensity.