A blacksmith is flattening a steel plate, 10 cm × 15 cm × 1 mm. He has heated the plate to 900 K. If the emissivity of the plate is 0.75, what is the total rate of radiation of energy? The Stefan-Boltzmann constant is 5.67 x 10^-8 W/(m²·K⁴). Ignore heat exchange with the surroundings.

Question

Quizplus · Accepted Answer

The total rate of radiation of energy can be calculated using the Stefan-Boltzmann law:

Q = εσAT⁴

Where:
Q = total rate of radiation of energy (in watts)
ε = emissivity of the plate
σ = Stefan-Boltzmann constant
A = surface area of the plate
T = temperature of the plate in Kelvin

Substituting the given values:

Q = (0.75)(5.67 × 10^-8)(0.1 × 0.15)(900)^4
Q ≈ 850 W

Therefore, the correct answer is D) 850 W.

A Blacksmith Is Flattening a Steel Plate, 10 Cm ×