Question

If a cup of coffee is at 90°C and a person with a body temperature of 36°C touches it, how will heat flow between them?

from the hand to the cup
from the cup to the hand
from the cup to the surrounding air
from the hand to surrounding air

Answer 1

Heat flows from hotter to colder. Since the cup is 90°C and the person’s hand is 36°C:

- From the cup to the hand (by conduction)
- From the cup to the surrounding air (by convection/radiation), provided the air is cooler than 90°C
- From the hand to the surrounding air if the air is cooler than 36°C

If the surrounding air were warmer than the hand (or warmer than the cup), the direction between that object and the air would reverse accordingly.