A1000-w iron is left on the ironing board with its base exposed to the air at 23◦c. the convection heat transfer coefficient between the base surface and the surrounding air is 20w/(m2◦c). if the base has an emissivity of 0.4 and a surface area of 0.02m2, determine the temperature of the base of the iron.

216.52°C

Explanation:

Hi,  in this problem we know the total heat transfer is 1000 W.

We need to do know is the surface temperature of the iron.

So we are going to use the equation for radiation heat transfer.

 So, we have the next data

A = 0.02 m^2

ε= 0.4

h = 20 W/m2·°C

T_∞ = 20°C.  

We can assume that the air temperature is Tsurfaces = 20°C = 293.15 K.  The Stefan-Boltzmann constant, σ = 5.670x10-8 W/m^2·K^4.  

Remember that we have to use Kelvin temperatures for the convection term

489.674K⇒216.52°C

  the   balanced   equation   for   reaction of   ca metal   with   o2 to   produce   cao   is as below

2 ca+ o2→ 2 cao2

  explanation

the reaction is   balanced     since the   number of atoms   in reactant side is   equal to   number of atoms   in   product side.   for   example   they   are 2   atom of   ca in   reactant   side   and   2   atoms of ca   in   the product side.

  the   process   is a   meet the   requirement   of   redox   reaction because :     calcium   is   oxidized   from   oxidation state 0   to 2+   while   oxygen   is reduced from   oxidation   state   0   to 2-

under a microscope, cancer cells may look very different from normal cells. they often have different sizes and some may be larger than normal while others are smaller. cancer cells are often abnormally shaped and the control centre of the cell (the nucleus) may have an abnormal appearance.

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