How Much Power Does a Sphere with a Radius of 10

question 28

Multiple Choice

How much power does a sphere with a radius of 10 cm radiate into empty space if is has an emissivity of 1.0 and is kept at a temperature of 400 K? (σ = 5.67 × 10^-8 W/m² ∙ K⁴)

• A)60 W
• B)70 W
• C)180 W
• D)210 W
• E)360 W