You put in a cold drink it stays cold
You put in a hot drink it stays hot
How does the THERMOS know what to do?
https://th.bing.com/th/id/R.54bd338932a124744cb40b68f7c90df6?rik=DERoSUJweyQ32Q&pid=ImgRaw
You put in a hot drink it stays hot
How does the THERMOS know what to do?
https://th.bing.com/th/id/R.54bd338932a124744cb40b68f7c90df6?rik=DERoSUJweyQ32Q&pid=ImgRaw