Microwaves and Metals

Microwave

From heating up the leftover meals to making popcorn, every time I open a microwave door, a little voice in the back of my head reminds me not to use any metal containers. Although I follow the advice every time, I never questioned the meaning behind it.

From heating up the leftover meals to making popcorn, every time I open a microwave door, a little voice in the back of my head reminds me not to use any metal containers. Although I follow the advice every time, I never questioned the meaning behind it.

Microwaves can pass through plastic, glass, or Styrofoam container to reach the food. However, molecules in metals are so densely packed that they prevent the microwaves from getting through. Thus, the waves just end up bouncing around the area and not cooking the food properly. They may even end up harming the appliance because of the endless bouncing.

This doesn’t explain the sparks we sometimes see when metal objects are placed in the microwave oven. It turns out that those sparks are simply caused by an electric field generated by the microwave oscillation. This electric field concentrates around any sharp objects or corners, similar to how a lightning rod protects our home from lightning. Sparks are visible when the electricity in the field discharges.

So, it’s that simple. I love science. Now the little voice in my head will also remind me of the reason behind not putting metals in the microwave oven. This concept was so simply and wonderfully explained by MIT School of Engineering.