Bell in Jar
Product Code : JL-LE-11370
The Bell in Jar (SKU JL-LE-11370, Cat. No. JSS-252/034) demonstrates that sound needs a medium to travel. An electric bell hangs inside an acrylic bell jar on a pump plate; as a vacuum pump removes the air, the ringing fades, and it grows louder again when air is let back in. It is supplied by JaincoLab for physics classes studying sound.
Specifications of the bell in jar apparatus
The construction details below come from the product listing.
| Product | Bell in Jar |
| SKU | JL-LE-11370 |
| Cat. No. | JSS-252/034 |
| Bell jar | Acrylic, with a flat flange |
| Pump plate | Lightweight aluminium on a heavy tripod base |
| Seal | Rubber sheet on the base; no vacuum grease needed |
| Evacuation | Tube connection through the central pillar |
| Stopcock | Seals the chamber so the vacuum holds with the pump off |
| Bell suspension | Wires, to reduce conduction of sound to the jar |
| Bell connection | 4 mm sockets on the top bung |
| Bell supply | 4 - 6 V DC or AC |
| Not included | Vacuum pump and heavy-walled vacuum tubing |
How the demonstration runs
A typical sequence with the bell in jar:
- Connect the bell to a 4 - 6 V supply through the 4 mm sockets and let the class hear it ring at normal pressure
- Evacuate the jar with a vacuum pump through the pillar connection and listen as the sound fades
- Close the stopcock, switch off and disconnect the pump, then let air back in slowly so the bell grows louder again
- Discuss why the bell hangs on wires: it limits sound carried through solid parts to the jar
Scope of supply and ordering
The listing covers the bell jar, pump plate with tripod base, stopcock and suspended bell. A suitable vacuum pump and heavy-walled vacuum/pressure tubing must be ordered separately; they can be added to the same quotation, which also confirms quantities, packing and lead time.
Frequently asked questions
Is a vacuum pump included?
No. The apparatus needs a suitable vacuum pump and heavy-walled vacuum/pressure tubing, which are ordered separately.
What voltage does the bell need?
The bell runs on 4 - 6 V, DC or AC, connected through 4 mm sockets on the top bung.
Does the base need vacuum grease?
No. A rubber sheet on the base seals the jar against the pump plate without grease.
Why is the bell suspended by wires?
Hanging the bell on wires reduces the sound conducted through solid parts to the jar, so the fading is easier to hear.
Related products
Other sound and pressure apparatus is in our laboratory equipment range.
Request a quote
For a quotation on the bell in jar, with or without a vacuum pump, use our contact page. Buying under a laboratory tender? Use our tenders page.
