Difficulty: Easy
Correct Answer: Disagree
Explanation:
Introduction / Context:
This item checks whether you can correctly associate classic heat-transfer laws with the proper mode: conduction, convection, or radiation. The Stefan–Boltzmann law is often misapplied outside radiation.
Given Data / Assumptions:
Concept / Approach:
The Stefan–Boltzmann law states that the total hemispherical emissive power of an ideal blackbody is E_b = σ * T^4. Net radiative exchange between real surfaces uses this as a basis with emissivity and view factors. Convection uses Newton’s law of cooling, q_conv = h * A * (T_s − T_∞), not T^4.
Step-by-Step Solution:
Identify the mode: Stefan–Boltzmann involves radiation.Write the form: q_rad = ε * σ * A * (T_s^4 − T_sur^4).Convection depends on film coefficient h, not σ, so the law does not apply to convection.
Verification / Alternative check:
Compare units: σ has units W/m^2·K^4, while h has units W/m^2·K. Different physics, different laws.
Why Other Options Are Wrong:
Common Pitfalls:
Confusing high-temperature convection with radiation; forgetting that radiation scales with the fourth power of absolute temperature.
Final Answer:
Disagree
Discussion & Comments