A human body is surrounded by air hotter than the body temperature. Considering convection, what is the algebraic sign of the 'heat loss from the body to the surroundings' under this condition?

Introduction / Context:
Convective heat transfer direction is driven by temperature difference between a surface and the surrounding fluid. Sign conventions matter in heat balance equations. The question asks for the sign of “heat loss from the body to the surroundings” when the surroundings are hotter than the body.

Given Data / Assumptions:

• Surrounding air temperature T_air > body surface temperature T_body.
• Standard sign convention: heat loss from the body is positive when heat leaves the body.

Concept / Approach:
Newton’s law of convection: q_conv = h * A * (T_surface − T_fluid). If T_fluid > T_surface, then (T_surface − T_fluid) is negative, meaning heat flows from the fluid to the body. Thus, when we specifically refer to “heat loss from the body,” its value is negative because the body is actually gaining heat, not losing it.

Step-by-Step Solution:

Verification / Alternative check:
Energy balance on the body shows net heat entering by convection when ambient is hotter; the same sign logic is used in HVAC load analysis and human thermal comfort models under hot-air exposure.

Why Other Options Are Wrong:

• Positive: Would imply body is hotter than air, which contradicts the condition.
• Zero: Only true when temperatures are equal or if h = 0 (not the case).
• Indeterminate / oscillatory: Unnecessary complexity; sign is fixed by temperature difference.

Common Pitfalls:
Reversing the temperature difference order or mixing up the definition of “loss” versus “gain.”

Final Answer:
Negative (body gains heat from surroundings)