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--- demonstrations:3_oscillations_and_waves:sound_waves:bell_in_a_vacuum:start [2019/02/14 23:33] – external edit 127.0.0.1
+++ demonstrations:3_oscillations_and_waves:sound_waves:bell_in_a_vacuum:start [2020/03/13 20:27] (current) – demoroom
@@ Line 1: / Line 1: @@
 ====== Bell In A Vacuum ======
-{{tag> needs_review untagged unlocated}}
+{{tag> oscillations_and_waves acoustics vacuum low_pressure bell_jar located}}
 <WRAP box right>
@@ Line 11: / Line 11: @@
 ===== Description =====
-Demonstrate that sound waves require a 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 a 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 =====
+Demonstrate that sound waves require a medium to travel.
-Show that sound waves require a medium to travel in
 ===== 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 =====
+  - 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 =====
+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>
@@ Line 65: / Line 51: @@
 </WRAP>
 <WRAP tablewidth 100%>
-| **Location** | ---- |
+| **Location** | C2 |
 | **Maker** | Unknown |
 | **Current State** | Working |