9. In which system is heat usually transferred from the cooler part to the warmer part?
a. A stove as it heats up water.
b. A refrigerator that is running.
c. An electric fan that is running.
d. None of the above, because it is impossible to transfer heat in this manner.
The correct answer is d. None of the above, because it is impossible to transfer heat in this manner.
Heat transfer usually occurs from a warmer region to a cooler region, not the other way around. It is a fundamental principle called the second law of thermodynamics. Heat naturally flows from areas of high temperature to areas of low temperature until thermal equilibrium is reached.
Let's understand why each option is not the correct answer:
a. A stove as it heats up water: When a stove heats water, the heat energy from the stove transfers to the water, increasing its temperature. Heat does not flow in the opposite direction, from the cooler water to the hotter stove. This option violates the second law of thermodynamics.
b. A refrigerator that is running: A refrigerator operates by removing heat from its interior and releasing it into the surrounding environment. It cools the inside of the fridge by transferring heat from the cooler space (inside) to the warmer space (outside). Heat transfer in this case also obeys the second law of thermodynamics since it occurs from a warmer region to a cooler region.
c. An electric fan that is running: An electric fan moves air around but does not cool it. It increases the rate of heat transfer by enhancing convection, but it does not transfer heat from a cooler region to a warmer region.
Therefore, the correct answer is d, none of the above. Heat transfer occurs from a warmer region to a cooler region according to the second law of thermodynamics.