Microwave ovens work by generating electromagnetic waves, specifically microwave radiation, to heat and cook food. These microwaves are absorbed by water, fats, and sugars present in the food, causing them to vibrate and generate heat. The heat then spreads throughout the food, cooking it from the inside out.
Metals, on the other hand, behave differently when exposed to microwave radiation. They reflect and repel microwaves rather than absorbing them. This is due to the high electrical conductivity of metals. When microwaves encounter metal surfaces, the electrons in the metal move rapidly in response to the changing electric field of the microwaves. This movement of electrons generates electric currents that produce their own electromagnetic fields, effectively canceling out the microwaves and preventing them from penetrating the metal.
As a result, metals do not heat up as quickly in a microwave oven compared to other materials that can absorb and convert microwave energy into heat. In fact, placing metal objects in a microwave can be hazardous as it may cause sparks, damage the microwave, or even start a fire due to the intense electrical currents generated.
To summarize, metals' high electrical conductivity causes them to reflect and repel microwave radiation, making them slow to heat up in a microwave oven compared to other materials that can efficiently absorb microwaves and convert them into heat.