how does the thermos keep my tea hot for several hours?
In: 30
Heat transfers out of the tea through conduction (colder thing touching the hot tea), convection (air moving over the hot tea), and radiation (hot tea sends out heat energy as light in frequencies too low for our eyes to see).
The thermos tries to reduce all three of these by having two metal walls (to reduce radiation) with all the air sucked out of the space in between (to prevent convection), and they’re only touching each other at the mouth of the thermos (to reduce conduction). The lid is also usually pretty thick with hollow parts inside it to act as insulation.
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