Question

What will happen if vacuum is filled with air in thermos flask

Answer 1

Answer:

Humans can be pretty contrary at the best of times. When it's cold, we want to warm up; when it's hot, we want to cool down. That's because we're warm-blooded creatures who need to keep our body temperatures more or less constant, at around 37°C (98.6°F), just to survive. Vacuum flasks are a bit like people in this respect: they like to keep things at steady temperatures. If you put hot drinks in them, they keep them hot; if you put cold drinks in them, they keep them cool. They're simple, neat, and effective—but how exactly do they work?