Thermostat puzzle

[From Rick Marken (951129.0750)]


... the thermostat experiment Bill Powers described recently.

Bill Powers (951129.0600 MST) --

You must be referring to an older post.

I was. Your puzzle from yesterday Bill Powers (951128.0805 MST) was:

So we found empirically that letting the sun shine into the room
caused the room to get colder! Can you guess what mechanism was
responsible for this negative effect of heat input on temperature

My guess would be that the apparently negative effect of heat on room
temperature was a result of the effect of the sunshine on the variable
controlled by the thermostat. Then the window was opened, the sunshine
heated the coil in the thermostat, making it expand to it's reference size
without the need for any heat output from the thermostat itself (the side-
effect of which heats the room). So the room got cold when the window was
opened to the sunshine because the thermostat is not controlling room
temperature; it's controlling the size of the coil (actually, the current
flow resulting from the electrical contact made when the coil explands). The
sunshine coming through the window caused the thermostat's coil to expand to
it's reference size before it had much effect on the temperature of the air
in the room; since the thermostat's heater went off (it was no longer needed
to keep the coil at the reference size) the room got cold.

i.kurtzer (951128.2200) and (951128.2200) --

S-R device or not, I think your recent posts have been exceptionally good.