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demonstrations:3_oscillations_and_waves:sound_waves:bell_in_a_vacuum:start [2019/02/14 23:33] external edit
demonstrations:3_oscillations_and_waves:sound_waves:bell_in_a_vacuum:start [2020/03/13 20:27] (current)
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 ====== Bell In A Vacuum ====== ====== Bell In A Vacuum ======
-{{tag> ​needs_review untagged unlocated}}+{{tag> ​oscillations_and_waves acoustics vacuum low_pressure bell_jar located}}
 <WRAP box right> <WRAP box right>
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 ===== Description ===== ===== Description =====
-Demonstrate that sound waves require ​medium ​to travel in   ​Classes Used: PHYS 101, 153 +This demonstration consists of a bell jar mounted on a platform. Inside the bell jar a sound source is hanging from support, and connected ​to a switch mounted external to the bell jar. The bell jar also has a fitting to attach a vacuum pump and a pressure release valve
- +
- +
- +
 ===== Purpose ===== ===== Purpose =====
- +Demonstrate ​that sound waves require a medium to travel
-Show that sound waves require a medium to travel ​in   +
- +
 ===== Apparatus ===== ===== Apparatus =====
- +  * Bell jar containing alarm and pressure gauge/​valves 
-Bell jar containing alarm and pressure gauge/​valves  +  * [[demonstrations:​9_equipment:​vacuum_pump_electric:​start|Vacuum pump]]
-Vacuum pump   +
- +
 ===== Setup ===== ===== Setup =====
- +  - Attach ​the vacuum ​pump hose to the connector on the demo. 
-Attach pump hose to nozzle ​ +  - Ensure that the valve on the vacuum pump hose is open, and that the pressure relief ​valve on the demo is closed. 
-Open intake ​valve and close outlet ​valve  +  ​- ​Turn on the alarm with the switch ​to demonstrate how loud it is. 
-Turn on the alarm via the switch  +  ​- ​Turn off the alarm and turn the pump on to evacuate ​the air in the jar. You can also just leave the alarm on during this step.  
-Turn off alarm and turn the pump on to evacuate the jar  +  - Once the vacuum has evacuated most of the air, close the valve on the vacuum pump hose, turn off the vacuum pump, and turn on the alarm back on. You should notice that it's dramatically ​quieter. 
-Turn alarm on again to demonstrate ​it has gotten much quieter  +  ​- ​Release outlet valve while alarm is on to show how it gets loud again when the air is reintroduced. ​
-Release outlet valve while alarm is on to show how it get'​s ​loud again  +
- +
 ===== Notes ===== ===== Notes =====
 +You will still hear a little noise from the alarm due to vibrations being transmitted by the supports inside the jar and the limits of the vacuum pump.
-You will still hear a little noise from the alarm due to vibrations and the limits ​of the vacuum ​pump  +Take care when handling this demo. The glass bell jar is probably only held to the platform by the stickiness ​of the vacuum ​grease and the gasket used to make a seal. 
-Valves are open in the vertical position (perpendicular ​to the pipe) and closed in the horizontal position  +
-Updated on: 06/19/13+
 <WRAP group> <WRAP group>
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 </​WRAP>​ </​WRAP>​
 <WRAP tablewidth 100%> <WRAP tablewidth 100%>
-| **Location** | ---- |+| **Location** | C2 |
 | **Maker** | Unknown | | **Maker** | Unknown |
 | **Current State** | Working | | **Current State** | Working |
demonstrations/3_oscillations_and_waves/sound_waves/bell_in_a_vacuum/start.1550187203.txt.gz · Last modified: 2019/02/14 23:33 by