Microwaves do not have a built-in mechanism to "know" when food is done in the same way that humans do. Instead, microwaves operate based on the principle of dielectric heating, where they emit electromagnetic waves (microwaves) that excite water molecules, fats, and sugars present in the food.
When you place food in the microwave and set a cooking time, the microwaves penetrate the food and cause water molecules to vibrate rapidly. This vibration generates heat, which cooks the food from the inside out. As the cooking time progresses, the temperature of the food rises until it reaches the desired level of doneness.
The microwave oven's control panel allows you to set the cooking time and, in some models, the power level. The cooking time determines how long the microwaves will be emitted, and the power level regulates the intensity of the microwaves. Lower power levels allow for more even cooking and prevent overheating certain parts of the food.
While microwaves do not have a sensor to detect doneness directly, some modern microwave models come with built-in sensors or smart technology. These sensors can measure the moisture or temperature inside the microwave during cooking. When the sensors detect a change in the food's properties or the humidity level, the microwave's circuitry may adjust the cooking time or power level to optimize the cooking process. This feature is often found in higher-end microwaves and can help ensure more accurate and consistent results.
For most microwaves, determining when food is done depends on the user's experience and judgment. It's essential to check the food's progress periodically during cooking, stir or rotate it if needed, and use recommended cooking times as a starting point. Over time, you'll become familiar with your microwave's performance and adjust your cooking habits accordingly to achieve the desired doneness.