Oxford Electric Bell
Encyclopedia
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...
al electric bell
Electric bell
An electric bell is a mechanical bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing or clanging sound...
that was set up in 1840 and which has rung almost continuously ever since. It is located in the foyer of the Clarendon Laboratory
Clarendon Laboratory
The Clarendon Laboratory, located on Parks Road with the Science Area in Oxford, England , is part of the Physics Department at Oxford University...
at the University of Oxford
University of Oxford
The University of Oxford is a university located in Oxford, United Kingdom. It is the second-oldest surviving university in the world and the oldest in the English-speaking world. Although its exact date of foundation is unclear, there is evidence of teaching as far back as 1096...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. it has been moved into an adjacent corridor due to building works but is still ringing, though inaudibly due to being behind two layers of glass.
The experiment consists of two brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
bells
Bell (instrument)
A bell is a simple sound-making device. The bell is a percussion instrument and an idiophone. Its form is usually a hollow, cup-shaped object, which resonates upon being struck...
, each positioned beneath a dry pile
Voltaic pile
A voltaic pile is a set of individual Galvanic cells placed in series. The voltaic pile, invented by Alessandro Volta in 1800, was the first electric battery...
(a form of battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
), the pair of piles connected in series. A metal sphere approximately 4 mm in diameter is suspended between the piles, and rings the bells by means of electrostatic force. As the clapper touches one bell, it is charged by one pile, and then electrostatically repelled, being attracted to the other bell. On hitting the other bell, the process repeats. The use of electrostatic forces means that while high voltage is required to create motion, only a tiny amount of charge is carried from one bell to the other, which is why the piles have been able to last since the apparatus was set up. Its oscillation frequency is 2 hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
.
Probably the most interesting part of the bell is the pair of dry piles. Nobody is certain what they are composed of, but it is known that they have been coated with molten sulphur to prevent effects from atmospheric
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
moisture and it is thought that they may be Zamboni pile
Zamboni pile
The Zamboni pile is an early electric battery, invented by Giuseppe Zamboni in 1812.A Zamboni pile is an "electrostatic battery" and is constructed from discs of silver foil, zinc foil, and paper...
s.
At one point this sort of device played an important role in distinguishing between two different theories of electrical action: the theory of contact tension (an obsolete scientific theory based on then-prevailing electrostatic principles) and the theory of chemical action
Electrochemistry
Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor and an ionic conductor , and which involve electron transfer between the electrode and the electrolyte or species in solution.If a chemical reaction is...
.
The Oxford Electric Bell does not demonstrate perpetual motion
Perpetual motion
Perpetual motion describes hypothetical machines that operate or produce useful work indefinitely and, more generally, hypothetical machines that produce more work or energy than they consume, whether they might operate indefinitely or not....
. The bell will eventually stop when the dry piles are depleted of charge — that is, if the clapper does not wear out first.
Further reading
- Willem Hackmann, "The Enigma of Volta's "Contact Tension" and the Development of the "Dry Pile"", appearing in Nuova Voltiana: Studies on Volta and His Times, nb Volume 3 (Fabio Bevilacqua; Lucio Frenonese (Editors)), 2000, pp. 103–119.