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When you touch something, you don't feel how hot/cold the thing is; you feel how hot/cold it makes your hand. Metal conducts heat more easily than wood. So if wood and metal are hot, the heat will flow more easily from the metal to your hand. If wood and metal are cold, the heat will flow more easily from your hand to the metal.


The two materials possess different thermal conductivities. The metal appears to have a higher temperature because the heat escapes it into your fingers quicker than the wood. http://en.wikipedia.org/wiki/Thermal_conductivity italicized part edited to not confuse future readers.


The heat flow (per unit area) through some thin layer, e.g. a boundary layer of water, is given by: $$ \frac{dQ}{dt} = \frac{K\Delta T}{d} $$ where $K$ is the thermal conductivity, $d$ is the thickness of the layer and $\Delta T$ is the temperature difference between the two sides of the layer. So a high thermal conductivity does indeed mean a high heat ...


Compare to the energy that the Earth surface receives from the sun, how much power comes from the inner melted core ? Very little. The Earth's surface emits about 503 watts per square meter (398.2 W/m2 as infrared radiation, 86.4 W/m2 as latent heat, and 18.4 W/m2 via conduction/convection), or about 260 petawatts over all of the Earth's surface ...


Heaters are one of the very few devices that are 100% efficient. All of the energy we put into them ends up as heat (though not all that heat may go where you want it to). So to a first approximation the energy used by your shower is determined by how hot you run the water and for how long, and it doesn't matter what heat setting you use. I say to a first ...

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