The diameter and surface emissivity of an electrically heated plate are d = 300 mm and ε = 0.80, respectively. (a) estimate the power needed to maintain a surface temperature of 200°c in a room for which the air and the walls are at 25°c. the coefficient characterizing heat transfer by natural convection depends on the surface temperature and, in units of w/m2.k, may be approximated by an expression of the form h=0.80(ts - too)1/3. (b) assess the effect of surface temperature on the power requirement, as well as on the relative contributions of convection and radiation to heat transfer from the surface.

The image compares the arrangement of electrons in two different neutral atoms. a figure labeled atom q has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has six black spheres. to the left of this figure is another figure labeled atom p. atom p has a shaded sphere at the center of three concentric circles. the innermost circle has two black spheres. the middle circle has seven black spheres. which of the following best explains the position of the two atoms in the periodic table? atom p has an estimated zeff of 7 and is therefore to the left of atom q, which has a zeff of 6. atom p has an estimated zeff of 7 and is therefore to the right of atom q, which has a zeff of 6. atom p has an estimated zeff of 5 and is therefore below atom q, which has a zeff of 4. atom p has an estimated zeff of 5 and is therefore above atom q, which has a zeff of 4.