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--- demonstrations:4_thermodynamics:4f_entropy_and_the_second_law:thermobile:start [2019/02/14 23:33] – external edit 127.0.0.1
+++ demonstrations:4_thermodynamics:4f_entropy_and_the_second_law:thermobile:start [2020/02/03 20:49] (current) – demoroom
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 ====== Thermobile ======
-{{tag> needs_review untagged unlocated}}
+{{tag> heat_engine thermodynamics shape_memory_effect nitinol unlocated}}
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 ===== Description =====
-Simple heat engine
+Stored in a small box with the branding 'Thermobile' on it. A plastic chassis connects two wheels, one bigger one made of plastic and a smaller one made of brass. Around them is a loop of nitinol- a shape memory alloy- that has been 'trained' to straighten when heated up.
-Dip the wheel into water ~60'C (requires an approximate 35'C temperature difference across the wheels) and wheels will start spinning. This simple engine work due to the metal wire regaining it straight shape when it reaches a warm temperature.   Updated on: 06/20/13
 ===== 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 =====
+  * 'Thermobile' Heat engine
+  * Cup of hot water (~60ºC)
+  * [[equipment:lab_stands:start|Lab stand and clamp]] (Optional)
 ===== Setup =====
+Dip the bottom edge of the brass wheel into the cup of hot water (this demo requires an approximate 35ºC temperature difference across the wheels to run), give the wheel a spin, and it should continue on it's own.
+It may be helpful to mount the thermobile on a lab stand so that the demo may be more easily shown.
 ===== Notes =====
+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.
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-| **Location** | ---- |
+| **Location** | C3 |
 | **Maker** | Unknown |
 | **Current State** | Working |