On Wed, Jun 7, 2017 at 1:07 AM, H LV <hveeder...@gmail.com> wrote: > animation explaining Joule's apparatus and his calculations. > > https://www.youtube.com/watch?v=5yOhSIAIPRE > > Harry > > On Tue, Jun 6, 2017 at 11:43 PM, H LV <hveeder...@gmail.com> wrote: >> >> >> Joule's apparatus used a spindle with paddles which was turned by a >> falling weight outside the calorimeter. The motion of the falling weight >> did not result in the generation of potential energy. It only resulted in >> the warming of the water inside calorimeter. However, if the falling of the >> weight were to wind up a spring in addition to turning of the paddle then >> the same energy input - in the form gravitational potential energy (i.e. >> the weight time the height through which the weight falls) would warm the >> water AND store energy in the spring. According to Joule the amount of heat >> generated is only a function of how far the weight falls. It is not a >> function of how quickly it falls, so even if the spring slows the descent >> of the weight the calorimeter will read the same rise in temperature with >> or without the spring attached. >> >> This thought experiment demonstrates how two systems can have the same >> energy input and generate the same temperatures but one can store energy >> and the other can't. >> >> t > > What I said above is not correct. In my thought experiment where I add a spring to Joule's original experiment (described in the video link given above) the amount of heat generated will be reduced because the weight will fall more slowly as it has to overcome both the resistance of the water and the spring. What needs to be emphasized is that Joule's original experiment implicitly assumes that the water does not store energy because the the amount of heat generated is claimed to be only dependent on the height the weight falls. Another way of stating this assumption is that all the resistance experienced by the falling weight is converted into thermal energy and none of it is stored energy.
Harry
