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Size: 2139
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Size: 3721
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| Deletions are marked like this. | Additions are marked like this. |
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| = Kundt's Tube = | = Kundt's Tube, 3D30.60 = |
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| * '''Bay:''' {A3 to A5} * '''Shelf:''' "T" |
* '''Bay:''' (A3 to A5) * '''Shelf:''' "T" |
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| attachment:KundtsTube3D3060-08.jpg | |
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| Kundt's tube is used to find the velocity of sound waves in a solid brass rod. The brass rod, which is fixed at its center, vibrates at its natural frequency when rubbed with a rosined cloth. The diaphragm at the end of the rod then excites the air molecules in the glass tube. By adjusting the plunger at the opposite end of the tube, standing waves are produced which activate some cork dust sprinkled along the length of the tube. The cork dust piles up at the displacement nodes which are separated a distance of l/2. From this measurement, the frequency of the sound waves can be determined. Since the rod is fixed at its center, its length represents l'/2 where l' is the wavelength of sound in the rod. Knowing the frequency (from the standing waves in air) and the wavelength l' in the rod, the velocity v' = fl' can be found. | The Kundt's tube can be used to find the velocity of sound waves in a solid brass rod. It also is a nice why to show standing waves in a pipe. The brass rod, which is fixed at its center, vibrates at its natural frequency when rubbed with a rosined cloth. The cork diaphragm at the end of the rod then excites the air molecules in the glass tube. By adjusting the tube, standing waves are produced which disturbs some cork dust that is sprinkled along the length of the tube. The cork dust then piles up at the displacement nodes which are separated by a distance of λ/2. From this measurement, the frequency of the sound waves can be determined. Since the rod is fixed at its center, its length represents λ'/2 where λ' is the wavelength of sound in the rod. Knowing the frequency (from the standing waves in air) and the wavelength λ' in the rod, the velocity ν' = ''f''λ' can be found. |
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| '''Equipment:''' 1. Kundt's Tube 1. Chamois or soft cloth 1. Powdered Rosin 1. Meterstick 1. Cork Dust (extra) 1. 2 Bench clamps |
||<:style="width: 60%" :40%>'''Equipment'''||<:30%>'''Location'''||<:25%>'''ID Number'''|| || || || || ||Kundt's Tube||(W&S) A3 to A5, Shelf "T"||5D30.60 || ||Chamois or soft cloth|| || || ||Rosin Powder|| || || ||2 Large C-clamps||Rode and Tack Cabinet|| || ||Meterstick|| In Lecture Halls|| || ||Extra Cork Dust|| Stock Cabinet || || ||Extra Rosin Powder|| Stock Cabinet || || |
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| 1. Check that there is enough cork dust in the tube. 1. Shake the tube so the cork dust is evenly distributed along its length. 1. Clamp the base of the apparatus to the lab bench so it doesn't move when the rod is being rubbed. |
1. To help student see, position a ceiling or external camera to observer the standing waves that form in the tube. 1. Clamp the base of the apparatus to the lab bench so it doesn't move when the rod is being rubbed. 1. Check that there is enough cork dust in the tube, if not add some from stock. 1. Slide glass tube out and gently shake it back-and-forth so the cork dust is evenly distributed along its length of tube. 1. Make absolutely sure that the cork diaphragm at the end of the brass rod is NOT touching the inner walls of the glass tube. The rod will not resonate if it is in contact with the tube. 1. The tube may need to be adjusted, moved back-and-forth to reach resonance. '''Cautions, Warnings, or Safety Concerns:''' 1. Brass rod can bend, popping the glass tube off it's supports. 1. Demonstration may require practice. 1. Resin powder will/can build up on the rod due to the heat from rubbing the rod. |
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| Sprinkle some resin powder on the Chamois or soft cloth, and rub the "end" half of the brass rod. While rubbing, have a volunteer from the class move the adjustable plunger until resonance occurs and the cork dust starts piling up at the nodes. Measure the distance between the piles of cork dust to give l/2. Since v in air is 33100 cm/sec, the frequency can be determined using f = v/l. The length of the brass rod (102 cm) gives the value of l'/2 in brass. Why? The fixed point of the rod forces a node in the center, and the free ends are antinodes. | Shake some resin powder on the Chamois or soft cloth and rub first 6" to 10" of the end of the brass rod. When rubbing use short pulling or pushing strokes with a good amount of pressure. If the cork diaphragm at the end of the brass rod is NOT touching the inner walls of the glass tube, the rod should start to sing. You will want to practice this before class to master your technique. While rubbing, have a volunteer from the class slide the glass tube back-and-forth until resonance occurs and the cork dust starts piling up at the nodes. Measure the distance between the piles of cork dust to give λ/2. Since v in air about 33100 cm/sec, the frequency can be determined by using ''f'' = ν/λ. Finally, since the length of the brass rod is 4 feet or 122 cm, we can calculate the value of λ'/2 in brass. Why? The fixed point of the rod forces a node in the center, and the free ends are antinodes. |
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Add photo.jpg here. |
||attachment:KundtsTube3D3060-06.jpg||attachment:KundtsTube3D3060-07.jpg|| ||attachment:KundtsTube3D3060-09.jpg||attachment:KundtsTube3D3060-10.jpg|| |
Kundt's Tube, 3D30.60
Location:
Cabinet: Waves & Sound
Bay: (A3 to A5)
Shelf: "T"
attachment:KundtsTube3D3060-08.jpg
Description:
The Kundt's tube can be used to find the velocity of sound waves in a solid brass rod. It also is a nice why to show standing waves in a pipe. The brass rod, which is fixed at its center, vibrates at its natural frequency when rubbed with a rosined cloth. The cork diaphragm at the end of the rod then excites the air molecules in the glass tube. By adjusting the tube, standing waves are produced which disturbs some cork dust that is sprinkled along the length of the tube. The cork dust then piles up at the displacement nodes which are separated by a distance of λ/2. From this measurement, the frequency of the sound waves can be determined. Since the rod is fixed at its center, its length represents λ'/2 where λ' is the wavelength of sound in the rod. Knowing the frequency (from the standing waves in air) and the wavelength λ' in the rod, the velocity ν' = fλ' can be found.
Equipment |
Location |
ID Number |
|
|
|
Kundt's Tube |
(W&S) A3 to A5, Shelf "T" |
5D30.60 |
Chamois or soft cloth |
|
|
Rosin Powder |
|
|
2 Large C-clamps |
Rode and Tack Cabinet |
|
Meterstick |
In Lecture Halls |
|
Extra Cork Dust |
Stock Cabinet |
|
Extra Rosin Powder |
Stock Cabinet |
|
Setup:
- To help student see, position a ceiling or external camera to observer the standing waves that form in the tube.
- Clamp the base of the apparatus to the lab bench so it doesn't move when the rod is being rubbed.
- Check that there is enough cork dust in the tube, if not add some from stock.
- Slide glass tube out and gently shake it back-and-forth so the cork dust is evenly distributed along its length of tube.
- Make absolutely sure that the cork diaphragm at the end of the brass rod is NOT touching the inner walls of the glass tube. The rod will not resonate if it is in contact with the tube.
- The tube may need to be adjusted, moved back-and-forth to reach resonance.
Cautions, Warnings, or Safety Concerns:
- Brass rod can bend, popping the glass tube off it's supports.
- Demonstration may require practice.
- Resin powder will/can build up on the rod due to the heat from rubbing the rod.
Demonstration:
Shake some resin powder on the Chamois or soft cloth and rub first 6" to 10" of the end of the brass rod. When rubbing use short pulling or pushing strokes with a good amount of pressure. If the cork diaphragm at the end of the brass rod is NOT touching the inner walls of the glass tube, the rod should start to sing. You will want to practice this before class to master your technique.
While rubbing, have a volunteer from the class slide the glass tube back-and-forth until resonance occurs and the cork dust starts piling up at the nodes. Measure the distance between the piles of cork dust to give λ/2. Since v in air about 33100 cm/sec, the frequency can be determined by using f = ν/λ. Finally, since the length of the brass rod is 4 feet or 122 cm, we can calculate the value of λ'/2 in brass. Why? The fixed point of the rod forces a node in the center, and the free ends are antinodes.
attachment:KundtsTube3D3060-06.jpg |
attachment:KundtsTube3D3060-07.jpg |
attachment:KundtsTube3D3060-09.jpg |
attachment:KundtsTube3D3060-10.jpg |
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