00:01
In this scenario, we have a cylindrical rod which is insulated on both sides and is between temperature baths at 300 degrees celsius and 30 degrees celsius.
00:11
Now, first thing we'll do is convert the temperature from celsius to kelvin.
00:16
So we'll simply add 273.
00:19
So 30 degrees celsius is 30 and 300 degrees celsius is 573 kelvin.
00:31
Now that we have this, because we want to find the entropy, remember that entropy is heat by temperature.
00:40
So first we need to find the heat flow.
00:42
So using the formula we found in the previous chapter, we remember that heat flow is thermal conductivity, times area, times change in temperature, which is the temperature difference divided by the length.
01:09
This quantity, the difference in temperature divided by length is called the temperature gradient.
01:16
We are making an approximation that the temperature changes gradually and linearly through the rod.
01:22
And that is it.
01:24
We can look up the conductivity of copper.
01:28
It's 401...