How does the 45 Tesla magnet work?

It's a hybrid system combining an outer superconducting electromagnet (11.5 Tesla) with an inner resistive magnet made of stacked thin plates (33.5 Tesla) to achieve a combined 45 Tesla.

Why are strong magnetic fields dangerous?

Strong fields can attract ferromagnetic objects with dangerous force, interfere with camera equipment, and pose extreme risks to anyone with metallic implants like pacemakers.

What is Lenz's Law and how does it affect falling objects?

Lenz's Law states that induced currents in a conductor oppose the change in magnetic flux. When a conductive plate falls through a magnetic field, Eddy currents are induced, creating an opposing magnetic field that slows its descent.

Can non-magnetic objects be levitated by this magnet?

Yes, diamagnetic materials like water, and by extension living organisms with high water content, can be repelled by strong magnetic fields and levitated.

Are strong magnetic fields safe for humans?

While there are no known long-term effects for brief exposures, strong fields can cause disorientation by affecting inner ear stones, and metallic implants pose a significant danger.

How are high-field magnets constructed?

They often use a hybrid approach, combining superconducting exteriors with resistive interiors. The resistive parts use stacked thin plates instead of wound wire to manage heat via axial cooling.

What are high magnetic fields used for in research?

They are crucial for material discovery by providing extreme environments (high magnetic fields, low temperatures, high pressures) to study or improve material properties.

World's Strongest Magnet!

Veritasium

Education6 min read24 min video

Mar 14, 2023|16,078,215 views|227,785|7,809

veritasium science physics

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Key Moments

TL;DR

World's strongest magnet at 45 Tesla utilizes superconducting and resistive tech, showcasing magnetic phenomena and energy use.

Key Insights

The world's strongest continuous magnetic field is 45 Tesla, nearly a million times Earth's field.

Achieving 45 Tesla requires a hybrid magnet: an outer superconducting magnet and an inner resistive magnet.

Strong magnetic fields can attract ferromagnetic objects and repulse or orient diamagnetic and paramagnetic materials.

Lenz's Law explains how changing magnetic fields induce eddy currents, opposing the change and causing deceleration or heating.

Superconductors, below their critical temperature, can levitate magnets by expelling magnetic fields.

Operating the 45 Tesla magnet consumes a significant amount of electricity, costing hundreds of thousands of dollars monthly.

THE POWER OF EXTREME MAGNETISM

The video introduces the world's strongest continuous magnetic field, generating an astonishing 45 Tesla. This field is a million times stronger than Earth's magnetic field and can exhibit dramatic effects, from attracting ferromagnetic objects with immense force to levitating non-magnetic items. The intense magnetic field also poses significant challenges for filming and camera equipment due to its disruptive influence on electronics, redirecting electron flow and causing potential damage. This remarkable magnetic strength is housed at the National High Magnetic Field Laboratory (NHMFL) in Tallahassee, Florida, which has held the Guinness World Record for the strongest continuous magnetic field since 2000.

HYBRID MAGNET TECHNOLOGY

Generating such an extreme magnetic field requires a sophisticated hybrid approach, combining two types of magnets. The system consists of an outer superconducting electromagnet and an inner resistive magnet. While superconducting magnets are limited to around 20 Tesla due to the field's effect on superconductivity, resistive magnets typically reach only about 2 Tesla. By integrating these two technologies, with the superconducting part providing a baseline field and the resistive part generating the bulk of the intensity, the NHMFL achieves its record-breaking 45 Tesla field. This dual-magnet system is essential for overcoming the limitations of each individual technology.

THE FRINGE EFFECT AND MAGNETIC INTERACTIONS

Even away from the magnet's core, its magnetic field, known as the fringe field, extends significantly. Objects within this fringe field, especially those with specific shapes, will orient themselves along the magnetic field lines. Ferromagnetic objects are strongly attracted and can be pulled into the magnet's bore if not secured. The video demonstrates this with a Nerf football containing steel washers, which is easily pulled towards the magnet. The danger of the fringe field is substantial, requiring strict protocols to prevent metallic objects or implants from entering the area when the magnet is active.

FERROFLUIDS AND THE ORIGINS OF MAGNETISM

The interaction of magnetic fields with ferrofluids, which contain nanoscale magnetite particles, is visually striking. When exposed to a magnetic field, these particles align, creating intricate patterns like parallel ridges and spikes. This phenomenon harkens back to the discovery of magnetism itself, which originated with naturally magnetized magnetite stones found in Magnesia, Greece, over 3,000 years ago. These 'loadstones' were observed to attract each other and iron, leading to the development of the compass and our understanding of magnetic poles.

THE SCIENCE OF MAGNETIC MATERIALS

The magnetic properties of materials are explained by the behavior of electrons. In most atoms, electrons are paired with opposite spins, canceling their magnetic fields. However, in elements with unpaired electrons, atoms possess magnetic fields. For a bulk material to be magnetic (ferromagnetic), these atomic magnetic fields must align within domains, and these domains must also align. This alignment can be induced by applying a strong external magnetic field, transforming non-magnetic materials into permanent magnets.

EDDY CURRENTS AND LENZ'S LAW IN ACTION

When conductive, non-ferromagnetic materials fall through a strong magnetic field, they experience induced electric currents known as eddy currents. According to Lenz's Law, these eddy currents generate their own magnetic field that opposes the change in flux, thereby impeding the material's motion. This can be observed as a significant deceleration of falling metal plates or cylinders. The energy from these eddy currents is dissipated as heat, which can be substantial enough to warm the material. This principle is also demonstrated by the difficulty in lifting a metal plate away from the magnet.

PARA- AND DIAMAGNETISM: LEVITATING THE UNEXPECTED

Beyond ferromagnetism, other magnetic behaviors are crucial for levitation. Paramagnetic materials, like liquid oxygen, are weakly attracted to magnetic fields. Diamagnetic materials, such as water, are weakly repelled. In sufficiently strong magnetic fields, this diamagnetic repulsion can be used to levitate objects like strawberries, raspberries, and even living organisms. The high water content in these items makes them diamagnetic enough to be suspended, demonstrating how advanced magnetic fields can overcome everyday material properties and provide insights into weightlessness.

SUPERCONDUCTORS AND MAGNETIC LEVITATION

Superconductors play a vital role in magnetic levitation. When cooled below their critical temperature, they exhibit zero electrical resistance and expel magnetic fields. If a magnet is brought near a superconductor, currents are induced that generate an opposing magnetic field, causing repulsion and levitation. The 'human levitator' demonstration shows a person standing on a magnet hovering above a ring of superconductors, illustrating the potential for stable and powerful magnetic suspension. Superconductors also possess defects that can trap magnetic fields, locking them in place.

THE ENGINEERING CHALLENGE OF RESISTIVE MAGNETS

Constructing the inner resistive magnet for the hybrid system is an engineering feat due to heat dissipation. Traditional wire-wound electromagnets overheat due to concentrated heat in inner windings. The solution involves shaping conductors into thin plates and stacking them with insulators. This creates channels for axial cooling, allowing much higher currents and thus stronger fields. The immense forces involved (20 tons of compression) require robust construction to maintain alignment and electrical connections. Even with these measures, material failures can occur, as seen in a coil that plastically deformed and destroyed adjacent coils.

ENERGY CONSUMPTION AND SCIENTIFIC DRIVERS

Operating the 45 Tesla magnet is tremendously energy-intensive, consuming a significant fraction of Tallahassee's electricity supply and costing hundreds of thousands of dollars monthly. This immense power is justified by its role in driving scientific discovery. Extreme environments, like high magnetic fields, are crucial for developing new materials or understanding existing ones by reducing impurities and enhancing properties. Researchers believe that the advancements enabled by facilities like the NHMFL will be seen as a pivotal point in material science in the coming decades.

SUSTAINABILITY AND GOOGLE'S EFFORTS

A portion of this video was sponsored by Google, highlighting the connection between magnets and future technologies like electric vehicles. Google's interest is rooted in sustainability, with the company matching 100% of its electricity use with renewable energy since 2017. Initiatives like Project Sunroof leverage Google Maps data to help homeowners assess the feasibility and savings of rooftop solar installations. The increasing search interest for sustainable technologies, as tracked by Google Trends, underscores a growing global focus on environmentally conscious solutions, with Google actively contributing to this transition.

Mentioned in This Episode

●Supplements

●Products

●Software & Apps

●Tools

●Companies

●Organizations

●Concepts

●People Referenced

Magnetic Field Strength Comparison

Data extracted from this episode

Object	Magnetic Field Strength (Tesla)	Note
Earth's Magnetic Field	0.00005	Reference value
Freely available magnet	0.1	Typical strong magnet
MRI Machine	Up to 3	Medical imaging
NHMFL Electromagnet	45	World's strongest continuous

Common Questions

The video features the 45 Tesla hybrid magnet at the National High Magnetic Field Laboratory in Tallahassee, Florida, which holds the Guinness World Record for the strongest continuous magnetic field.

Topics

Strongest Magnet Magnetic Field Strength Lenz's Law Eddy Currents Diamagnetism Paramagnetism High Magnetic Field National High Magnetic Field Laboratory Ferromagnetism

Mentioned in this video

organizationNational High Magnetic Field Laboratory

The location where the world's strongest continuous magnetic field is held, featuring a 45 Tesla hybrid magnet.

productResistive magnet

An inner component of the 45 Tesla magnet made of ordinary wire, producing 33.5 Tesla, requiring significant cooling.

productPacemaker

A medical device that is a metallic implant and therefore extremely dangerous to have near a strong magnetic field.

productFerrofluid

A liquid containing nanoscale pieces of magnetite that aligns with magnetic fields, forming intricate patterns.

conceptMagnetite

An iron-containing mineral, the first naturally magnetic material discovered, and the origin of the word 'magnet'.

conceptElectrons

Tiny magnets within atoms that, when paired, cancel out their fields. Unpaired electrons in half-full shells can create atomic magnetic fields.

softwareProject Sunroof

A Google tool that uses Google Maps data to help homeowners assess the feasibility and savings of rooftop solar panels.

conceptEddy currents

Electric currents induced within conductors by a changing magnetic field, which create their own magnetic fields that oppose the change.

toolPotato cannon

Used to fire projectiles across the magnetic field to measure deceleration and the effects of Eddy currents on orientation.

productLEDs

Connected to coils in projectiles, these light up when crossing the magnetic field, indicating the presence and direction of induced currents.

conceptSuperconductor

A material with zero electrical resistance below its critical temperature, allowing induced currents to persist indefinitely and expel magnetic fields.

conceptDiamagnetism

A property of most materials where they are repelled by a strong magnetic field. Water is a prime example.

productStrawberry

Demonstrated to be diamagnetic and levitated in a strong enough magnetic field due to its high water content.

productSuperconducting magnet

An outer component of the 45 Tesla magnet that produces 11.5 Tesla, limited by the field strength it can withstand.

productNerf football

Used in an experiment to demonstrate magnetic attraction, with steel washers hidden inside to make it stick to the magnet.

locationMagnesia

A region in Greece where naturally magnetized pieces of magnetite were first found, giving rise to the word 'magnet'.

productCompass needle

An application of magnets historically realized in China by the 11th century to always point in the same direction (North).

conceptPlastic

One of the non-ferromagnetic materials tested, which falls normally through the magnetic field, unlike conductive materials.

softwareGoogle Trends

A tool used by Google to track search interest, which showed an all-time high for electric vehicles in the last 12 months.

conceptLenz's Law

The principle stating that induced electric currents in a conductor oppose the change in magnetic flux that created them, causing effects like slowing down falling metal plates.

productElectromagnetic levitator

A device at the Palace of Discovery in Paris that uses alternating current to levitate a plate, generating significant heat from Eddy currents.

productAluminum foil

Used to wrap a volleyball, which was then dropped into the magnet, demonstrating the effect of Eddy currents slowing down conductive materials.

productHuman levitator

A demonstration involving a 90 lb magnet hovering above a ring of superconductors due to the interaction of magnetic fields.

personFrancis Bitter

An MIT physicist who realized that conductors could be formed into thin plates and stacked to improve cooling and achieve higher currents in electromagnets.

toolTesla

supplementCopper