The Oxford Electric Bell or Clarendon Dry Pile is an

experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into Causality, cause-and-effect by demonstrating what outcome oc ...

electric bell An electric bell is a mechanical or electronic bell that functions by means of an electromagnet. When an electric current is applied, it produces a repetitive buzzing, clanging or ringing sound. Electromechanical bells have been widely used at r ...

, in particular a type of bell that uses the electrostatic clock principle that was set up in 1840 and which has run nearly continuously ever since. It was one of the first pieces purchased for a collection of apparatus by clergyman and physicist Robert Walker. It is located in a corridor adjacent to the foyer of the

Clarendon Laboratory The Clarendon Laboratory, located on Parks Road within the Science Area in Oxford, England (not to be confused with the Clarendon Building, also in Oxford), is part of the Department of Physics at Oxford University. It houses the atomic and ...

at the

University of Oxford , mottoeng = The Lord is my light , established = , endowment = £6.1 billion (including colleges) (2019) , budget = £2.145 billion (2019–20) , chancellor ...

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...

, and is still ringing, albeit inaudibly due to being behind two layers of glass.

Design

The experiment consists of two

brass Brass is an alloy of copper (Cu) and zinc (Zn), in proportions which can be varied to achieve different mechanical, electrical, and chemical properties. It is a substitutional alloy: atoms of the two constituents may replace each other with ...

bells, each positioned beneath a dry pile (a form of

battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

), the pair of piles connected in

series Series may refer to: People with the name * Caroline Series (born 1951), English mathematician, daughter of George Series * George Series (1920–1995), English physicist Arts, entertainment, and media Music * Series, the ordered sets used in ...

, giving the bells opposite

electric charge Electric charge is the physical property of matter that causes charged matter to experience a force when placed in an electromagnetic field. Electric charge can be ''positive'' or ''negative'' (commonly carried by protons and electrons respe ...

s. The clapper is a metal sphere approximately in diameter suspended between the piles, which rings the bells alternately due to

electrostatic force Coulomb's inverse-square law, or simply Coulomb's law, is an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles. The electric force between charged bodies at rest is convention ...

. When the clapper touches one bell, it is charged by that pile. It is then repelled from that bell due to having the same charge and attracted to the other bell, which has the opposite charge. The clapper then touches the other bell and the process reverses, leading to

oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendulum ...

. The use of electrostatic forces means that while high

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...

is required to create motion, only a tiny amount of charge is carried from one bell to the other. As a result, the batteries drain very slowly, which is why the piles have been able to last since the apparatus was set up in 1840. Its oscillation frequency is 2

hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...

. The exact composition of the dry piles is unknown, but it is known that they have been coated with molten

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

for insulation and it is thought that they may be

Zamboni pile The Zamboni pile (also referred to as a ''Duluc Dry 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. A ...

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 Contact electrification is a phrase that describes a phenomenon whereby surfaces become electrically charged, via a number of possible mechanisms, when two or more objects come within close proximity of one another. When two objects are "touched" ...

(an

obsolete scientific theory This list catalogs well-accepted theories in science and pre-scientific natural philosophy and natural history which have since been superseded by scientific theories. Many discarded explanations were once supported by a scientific consensus, b ...

based on then-prevailing electrostatic principles) and the theory of chemical action. The Oxford Electric Bell does not demonstrate

perpetual motion Perpetual motion is the motion of bodies that continues forever in an unperturbed system. A perpetual motion machine is a hypothetical machine that can do work infinitely without an external energy source. This kind of machine is impossible, a ...

. The bell will eventually stop when the dry piles have distributed their charges equally if the clapper does not wear out first. The Bell has produced approximately 10 billion rings since 1840 and holds the Guinness World Record as "the world's most durable battery eliveringceaseless

tintinnabulation {{Short pages monitor