In winter Sunita feels warm in a sweater
In winter Sunita feels warm in a sweater. She says the sweater makes heat and gives it to her body. Her friend says she does stay warm but the reason is wrong. Who is thinking correctly?
Who do you think is right? Pick one.
The answer: It only traps her own heat
Why
Sunita's right that the sweater keeps her warm — the warmth is real, so it's easy to think the sweater is making it. But a sweater has no source of heat; lying on a chair it stays cold, never warming the room. YOUR body is the heater — food gives you warmth all the time, and normally it escapes into cold air. The sweater's woolly fibres trap tiny pockets of still air that hold your own heat close instead of letting it flee. It doesn't add heat; it slows heat from leaving. Test: wrap a sweater around a cold water bottle and it stays cold — no body heat inside to keep, nothing for the wool to trap. Her friend is right: the sweater only traps the heat Sunita already makes, it doesn't create any.
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