Physics
Physics
Problem
Blocks A and B are placed in thermal contact. Initially, block A is at 80 °C and block B is at 20 °C. After contact, 200 J of energy is transferred from A to B. Using the sign convention that when energy enters a system, state the value (including sign) of for each block and classify the process for each block as heating or cooling.Intuitive explanation
Heat flow is fundamentally about energy transfer direction: when blocks touch, the hotter one loses energy while the cooler one gains it. The sign convention is your guide—use positive for energy entering a system and negative for energy leaving it. Block A is the source, losing 200 J, while block B is the receiver, gaining those same 200 J; classify each process based on whether temperature rises or falls.
Intuitive explanation
Heat flow is fundamentally about energy transfer direction: when blocks touch, the hotter one loses energy while the cooler one gains it. The sign convention is your guide—use positive for energy entering a system and negative for energy leaving it. Block A is the source, losing 200 J, while block B is the receiver, gaining those same 200 J; classify each process based on whether temperature rises or falls.