A Bitter electromagnet or Bitter solenoid is a type of electromagnet

Electromagnet

An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...

 used in scientific research to create extremely strong magnetic field

Magnetic field

A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

s. It is constructed of circular metal

Metal

A metal , is an element, compound, or alloy that is a good conductor of both electricity and heat. Metals are usually malleable and shiny, that is they reflect most of incident light...

 plates and insulating

Electrical insulation

thumb|250px|[[Coaxial Cable]] with dielectric insulator supporting a central coreThis article refers to electrical insulation. For insulation of heat, see Thermal insulation...

 spacers stacked in a helical

Helix

A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...

 configuration, rather than coils of wire. This design was invented in 1933 by American physicist Francis Bitter

Francis Bitter

Francis Bitter was an American physicist.Bitter invented the Bitter plate used in resistive magnets . He is the one who thought of using dust to visualize a magnetic field...

. In his honor the plates are known as Bitter plates. Bitter electromagnets have been used to produce some of the strongest continuous manmade magnetic field

Magnetic field

A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

s on earth (up to 35 teslas

Tesla (unit)

The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...

  as of 2008).

The purpose of the stacked plate design is to withstand the enormous outward mechanical pressure produced by Lorentz force

Lorentz force

In physics, the Lorentz force is the force on a point charge due to electromagnetic fields. It is given by the following equation in terms of the electric and magnetic fields:...

s, which increase with the square of the magnetic field strength. Additionally, water circulates through holes in the plates as a coolant

Coolant

A coolant is a fluid which flows through a device to prevent its overheating, transferring the heat produced by the device to other devices that use or dissipate it. An ideal coolant has high thermal capacity, low viscosity, is low-cost, non-toxic, and chemically inert, neither causing nor...

, to carry away the enormous heat created in the plates due to resistive heating

Joule heating

Joule heating, also known as ohmic heating and resistive heating, is the process by which the passage of an electric current through a conductor releases heat. It was first studied by James Prescott Joule in 1841. Joule immersed a length of wire in a fixed mass of water and measured the temperature...

 by the large currents flowing through them. The heat dissipation also increases with the square of the magnetic field strength. The strongest continuous manmade magnetic field, 45 T, was produced by a device consisting of a Bitter magnet inside a superconducting magnet

Superconducting magnet

A superconducting magnet is an electromagnet made from coils of superconducting wire. They must be cooled to cryogenic temperatures during operation. In its superconducting state the wire can conduct much larger electric currents than ordinary wire, creating intense magnetic fields...

.

Despite the drawback of resistive heating, Bitter electromagnets are used where extremely strong fields are required because superconducting

Superconductivity

Superconductivity is a phenomenon of exactly zero electrical resistance occurring in certain materials below a characteristic temperature. It was discovered by Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum...

 electromagnets

Superconducting magnet

A superconducting magnet is an electromagnet made from coils of superconducting wire. They must be cooled to cryogenic temperatures during operation. In its superconducting state the wire can conduct much larger electric currents than ordinary wire, creating intense magnetic fields...

 cannot operate above the field strength at which the magnet materials cease to be superconducting (typically on the order of 10 to 20 teslas, due to flux creep

Flux pinning

Flux pinning is the phenomenon that magnetic flux lines do not move in spite of the Lorentz force acting on them inside a current-carrying...

, though theoretical limits are higher).

Largest Bitter magnet

As of 2011 the National High Magnetic Field Laboratory in Tallahassee, Florida, USA, houses the current world's largest resistive magnet. This system has a maximum output of 36.2 teslas and consists of hundreds of separate Bitter plates. The system consumes 19.6 megawatts of electric power and requires about 139 litres of water pumped through it per second for cooling. . This magnet is mainly used for material science experimentation. For similarly designed examples of bitter coils see the external links below.

External links

• National High Magnetic Field Laboratory Magnet Projects Page at Florida State University
  Florida State University
  The Florida State University is a space-grant and sea-grant public university located in Tallahassee, Florida, United States. It is a comprehensive doctoral research university with medical programs and significant research activity as determined by the Carnegie Foundation...
  
  
• Magnets at Nijmegen High Field Magnet Laboratory
• The Frog That Learned to Fly and a ball of water inside a Bitter solenoid at the High Field Magnet Laboratory
• Diagrams and description of the Bitter solenoid used in the frog levitation demonstration
• Bitter magnet designs: NHMFL Bitter Magnet and Radbound University Bitter Solenoid