Which thermometer is least effective for thin foods?

Bimetal thermometers are designed for measuring the temperature of thicker foods because they require a certain amount of food mass around their sensing area to provide an accurate reading. Their dial and probe construction responds more slowly to temperature changes, making them less effective for thin foods, where the temperature can change rapidly.

Thermistor thermometers, on the other hand, use an electronic sensor to quickly measure temperature and are generally suited for both thin and thick foods, allowing for more precise readings. Infrared thermometers measure surface temperature without needing to come into contact with the food, making them very effective for thin items, as they can provide instant readings without affecting the food. Liquid-filled thermometers, such as those that use mercury or alcohol, can also be adequate for thin foods, as they measure temperature more quickly than bimetal types.

In summary, since bimetal thermometers require a thicker mass of food to function properly, they are the least effective option for thin foods among the choices provided.