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--- demonstrations:4_thermodynamics:4f_entropy_and_the_second_law:nitinol_windmill:start [2019/02/14 23:33] – external edit 127.0.0.1
+++ demonstrations:4_thermodynamics:4f_entropy_and_the_second_law:nitinol_windmill:start [2019/04/17 19:30] (current) – demoroom
@@ Line 1: / Line 1: @@
 ====== Nitinol Windmill ======
-{{tag> needs_review untagged unlocated}}
+{{tag> heat_engine thermodynamics shape_memory_effect nitinol unlocated}}
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@@ Line 11: / Line 11: @@
 ===== Description =====
-Perpetual Motion Machine?    Classes Used: PHYS 153
+A chassis connects two wheels of equal size. Around them is a loop of nitinol- a shape memory alloy- that has been 'trained' to straighten when heated up. The top wheel has a propeller attached.
-This works off a temperature gradient across the Nitinol wire, and boiling water (or close to, about ~90) is usually good enough for a room temperature environment. Submerge the bottom wheel into said boiling water (just enough to cover the wire) and give the blades a small flick to start.
 ===== Purpose =====
+Illustrate another example of the huge variety of heat engines. Demonstrate the action of a much simpler heat engine, and show what unites all heat engines: a heat differential.
 ===== Apparatus =====
+  * Nitinol windmill
+  * Cup of nearly boiling water
 ===== Setup =====
+This works off a temperature gradient across the Nitinol wire, and boiling water (or close to, ~90ºC) is usually good enough for a room temperature environment. Submerge the bottom wheel into the boiling water (just enough to cover the wire) and give the blades a small flick to start it.
+===== Notes =====
-===== Notes =====
+The one with tape on its supporting beam doesn't work as well. There is also a cup near the windmills that has tearing to indicate the maximum filling line.
-The one with tape on its supporting beam doesn't work as well. There is also a cup near the windmills that has tearing to indicate the maximum filling line.  Updated on 05/30/13
+This simple engine works using a more complicated principle: the [[wp>Shape-memory_alloy|shape memory effect]]. When the wire is bent around a wheel and heated, it will exert a force attempting to straighten itself out. Once the wheel is given a spin, a temperature asymmetry will cause more force to be exerted on one side of the thermobile, so it continues to spin.
 <WRAP group>