Earth's magnetic field is about 25-65 microtesla (0.25-0.65 Gauss) at the surface—enough to deflect compass needles

A refrigerator magnet produces about 0.001 Tesla (10 Gauss) at its surface

MRI machines use 1.5 to 7 Tesla—up to 140,000× stronger than Earth's field!

The strongest continuous magnetic field ever created in a lab: 45.5 Tesla (Florida State University)

Neutron stars have magnetic fields up to 100 million Tesla—the strongest in the universe

The human brain produces magnetic fields of about 1-10 picotesla, measurable by MEG scans

Maglev trains use magnetic fields of 1-4 Tesla to levitate and propel trains at 600+ km/h

1 Tesla = 10,000 Gauss exactly (defined relationship between SI and CGS systems)

Definition: SI unit of magnetic flux density. 1 T = 1 Weber/m² = 1 kg/(A·s²)

Named after: Nikola Tesla (1856-1943), inventor and electrical engineer

Usage: MRI machines, research magnets, motor specifications

Typical values: Earth: 50 µT | Fridge magnet: 10 mT | MRI: 1.5-7 T

Definition: CGS unit of magnetic flux density. 1 G = 10⁻⁴ T = 100 µT

Named after: Carl Friedrich Gauss (1777-1855), mathematician and physicist

Usage: Older equipment, geophysics, industrial gaussmeters

Typical values: Earth: 0.5 G | Speaker magnet: 1-2 G | Neodymium magnet: 1000-3000 G

Definition: SI unit of magnetic field strength. Current per unit length that creates the field.

Usage: Electromagnet design, coil calculations, magnetic materials testing

Typical values: Earth: 40 A/m | Solenoid: 1000-10000 A/m | Industrial magnet: 100 kA/m

Definition: CGS unit of magnetic field strength. 1 Oe = 79.5775 A/m

Named after: Hans Christian Ørsted (1777-1851), discovered electromagnetism

Usage: Magnetic recording, permanent magnet specifications, hysteresis loops

Typical values: Hard disk coercivity: 2000-4000 Oe | Permanent magnet: 500-2000 Oe

Definition: One millionth of a Tesla. 1 µT = 10⁻⁶ T = 0.01 G

Usage: Geophysics, navigation, EMF measurements, biomagnetism

Typical values: Earth's field: 25-65 µT | Brain (MEG): 0.00001 µT | Power lines: 1-10 µT

Definition: Equal to 1 nanotesla. 1 γ = 1 nT = 10⁻⁹ T. Used in geophysics.

Usage: Magnetic surveys, archaeology, mineral exploration

Typical values: Magnetic anomaly detection: 1-100 γ | Daily variation: ±30 γ

Electromagnetism

During a lecture demonstration, Ørsted noticed a compass needle deflecting near a current-carrying wire. This was the first observation linking electricity and magnetism. He published his findings in Latin, and within weeks, scientists across Europe were replicating the experiment.

Proved that electric currents create magnetic fields, founding the field of electromagnetism

Electromagnetic induction

Faraday discovered that changing magnetic fields create electric currents. Moving a magnet through a coil of wire generated electricity—the principle behind every electric generator and transformer today.

Made possible electric power generation, transformers, and the modern electrical grid

Unified electromagnetic theory

Maxwell's equations unified electricity, magnetism, and light into one theory. He introduced the concepts of B-field and H-field as distinct quantities, showing light is an electromagnetic wave.

Predicted electromagnetic waves, leading to radio, radar, and wireless communication

Lorentz force law

Described the force on a charged particle moving in magnetic and electric fields: F = q(E + v × B). This formula is fundamental to understanding how motors, particle accelerators, and cathode ray tubes work.

Foundation for understanding particle motion in fields, mass spectrometry, and plasma physics

Superconductivity

Cooling mercury to 4.2 K, Onnes discovered its electrical resistance vanished completely. Superconductors expel magnetic fields (Meissner effect), enabling ultra-strong magnets with zero energy loss.

Led to MRI machines, maglev trains, and particle accelerator magnets producing 10+ Tesla fields

First laser

While not directly about magnetism, lasers enabled precise magnetic field measurements through magneto-optical effects like Faraday rotation and the Zeeman effect.

Revolutionized magnetic field sensing, optical isolators, and magnetic data storage

MRI medical imaging

Damadian discovered that cancerous tissue has different magnetic relaxation times than healthy tissue. This led to MRI (Magnetic Resonance Imaging), using 1.5-7 Tesla fields to create detailed body scans without radiation.

Transformed medical diagnostics, enabling non-invasive imaging of soft tissues, brain, and organs

Verdict: FALSE

Both measure the same thing (B-field/flux density), just in different unit systems. Tesla is SI, Gauss is CGS. 1 T = 10,000 G exactly. They're as interchangeable as meters and feet.

Verdict: CONDITIONAL

Only true in vacuum/air! In magnetic materials, the conversion depends on permeability μᵣ. In iron (μᵣ~2000), 1000 A/m creates 2.5 T, not 0.00126 T. Always state your assumption when converting B ↔ H.

Verdict: MOSTLY FALSE

Static magnetic fields up to 7 Tesla (MRI machines) are considered safe. Your body is transparent to static magnetic fields. Concern exists for extremely rapidly changing fields (induced currents) or fields above 10 T. Earth's 50 µT field is completely harmless.

Verdict: AMBIGUOUS

Confusing! In physics, 'magnetic field strength' specifically means H-field (A/m). But colloquially, people say 'strong magnetic field' meaning high B-field (Tesla). Always clarify: B-field or H-field?

Verdict: FALSE (BUT CLOSE)

In vacuum: 1 Oe ≈ 1 G numerically, BUT they measure different quantities! Oersted measures H-field (magnetizing force), Gauss measures B-field (flux density). It's like confusing force with energy—they happen to have similar numbers in air, but they're physically different.

Verdict: DEPENDS

Typical electromagnets: 0.1-2 T. Neodymium magnets: 1-1.4 T surface field. But superconducting electromagnets can reach 20+ Tesla, far exceeding any permanent magnet. Electromagnets win for extreme fields; permanent magnets win for compactness and no power consumption.

Verdict: FALSE

Magnetic fields penetrate most materials easily! Only superconductors completely expel B-fields (Meissner effect), and high-permeability materials (mu-metal) can redirect field lines. This is why magnetic shielding is difficult—you can't just 'block' fields like you can with electric fields.

Range: 1 µT to 10 T

Accuracy: ±1-5%

Measures: B-field (Tesla/Gauss)

Most common. Semiconductor chip that outputs voltage proportional to B-field. Used in smartphones (compass), gaussmeters, and position sensors.

Pros: Inexpensive, compact, measures static fields

Cons: Temperature sensitive, limited accuracy

Range: 0.1 nT to 1 mT

Accuracy: ±0.1 nT

Measures: B-field (Tesla)

Uses saturation of magnetic core to detect tiny field changes. Used in geophysics, navigation, and space missions.

Pros: Extremely sensitive, great for weak fields

Cons: Cannot measure high fields, more expensive

Range: 1 fT to 1 mT

Accuracy: ±0.001 nT

Measures: B-field (Tesla)

Most sensitive magnetometer. Requires liquid helium cooling. Used in MEG brain scans and fundamental physics research.

Pros: Unmatched sensitivity (femtotesla!)

Cons: Requires cryogenic cooling, very expensive

Range: 10 µT to 10 T

Accuracy: ±2-10%

Measures: Change in B-field (dB/dt)

Coil of wire that generates voltage when flux changes. Cannot measure static fields—only AC or moving fields.

Pros: Simple, robust, high-field capable

Cons: Only measures changing fields, not DC

Range: 1 A to 1 MA

Accuracy: ±1%

Measures: Current (related to H-field)

Measures AC current by detecting the magnetic field it creates. Wraps around a conductor without contact.

Pros: Non-invasive, wide dynamic range

Cons: AC only, doesn't measure field directly

Tesla (T) is the SI unit, Gauss (G) is the CGS unit. 1 Tesla = 10,000 Gauss exactly. Tesla is preferred for scientific and medical applications, while Gauss is still common in older literature and some industrial contexts.

Only in vacuum/air! In vacuum: B (Tesla) = μ₀ × H (A/m) where μ₀ = 4π×10⁻⁷ ≈ 1.257×10⁻⁶ T·m/A. In magnetic materials like iron, you need the material's relative permeability (μᵣ), which can be 1 to 100,000+. Our converter assumes vacuum.

B-field (flux density) measures the actual magnetic force experienced, including material effects. H-field (field strength) measures the magnetizing force that creates the field, independent of material. In vacuum B = μ₀H, but in materials B = μ₀μᵣH where μᵣ varies enormously.

Earth's field ranges from 25-65 microtesla (0.25-0.65 Gauss) at the surface. It's weakest at the equator (~25 µT) and strongest at the magnetic poles (~65 µT). This is strong enough to orient compass needles but 20,000-280,000× weaker than MRI machines.

Yes! 1 Tesla is about 20,000× stronger than Earth's field. Refrigerator magnets are ~0.001 T (10 G). MRI machines use 1.5-7 T. The strongest lab magnets reach ~45 T. Only neutron stars exceed millions of Tesla.

1 Oersted (Oe) = 1000/(4π) A/m ≈ 79.577 A/m. Oersted is the CGS unit for H-field, while A/m is the SI unit. The conversion factor comes from the definition of the ampere and CGS electromagnetic units.

International standards (IEC, FDA) require Tesla for medical imaging. It avoids confusion (1.5 T vs 15,000 G) and aligns with SI units. MRI safety zones are defined in Tesla (0.5 mT, 3 mT guidelines).

Static fields >1 T can interfere with pacemakers and pull ferromagnetic objects (projectile hazard). Time-varying fields can induce currents (nerve stimulation). MRI safety protocols strictly control exposure. Earth's field and typical magnets (<0.01 T) are considered safe.