Tesla (unit)

The tesla (symbol: T) is the unit used to measure magnetic flux density, also called the magnetic B-field, in the International System of Units (SI). This helps scientists and engineers describe how strong a magnetic field is.

One tesla equals one weber per square metre. This unit was announced in 1960 during the General Conference on Weights and Measures. It is named to honor Nikola Tesla, a talented Serbian-American electrical and mechanical engineer. The idea to name the unit after him was proposed by another engineer named France Avčin from Slovenia.

Definition

The tesla is a unit that measures how strong a magnetic field is. It was named after Nikola Tesla, a scientist who worked with electricity.

One tesla means that a tiny piece of electric charge moving through a magnetic field feels a certain amount of push or pull. The tesla is part of the International System of Units, which is the standard way scientists around the world measure things. Its symbol is a capital "T".

Electric vs. magnetic field

In science, electric fields and magnetic fields work in different ways. A magnetic field only affects a charged particle if that particle is moving, while an electric field can affect a charged particle even when it is standing still. The unit for an electric field is newtons per coulomb (N/C), while the unit for a magnetic field, called the tesla, can be written as N/(C⋅m/s).

In certain materials called ferromagnets, the movement of tiny particles called electrons creates the magnetic field. In wires that carry electric current, the movement of electrons through the wire creates the magnetic field.

Conversion to non-SI units

One tesla can also be measured in different ways. It equals 10,000 gauss, a unit used in the CGS system. It also equals one billion gamma, a unit used in geophysics.

For more information about how this relates to magnetising field units, see the article on permeability.

Multiples

The tesla is the unit we use to measure magnetic flux density, which tells us how strong a magnetic field is.

Sometimes we need smaller or larger versions of the tesla to describe very weak or very strong magnetic fields. For this, we use multiples of the tesla.

Here are some common multiples:

Examples

Main article: Orders of magnitude (magnetic field)

Here are some examples of magnetic field strengths, listed from weakest to strongest:

• 3.2×10⁻⁵ T – strength of Earth's magnetic field
• 4×10⁻⁵ T – walking under a high-voltage power line
• 5×10⁻³ T – strength of a typical refrigerator magnet
• 0.3 T – strength of solar sunspots
• 1 T to 2.4 T – coil gap of a typical loudspeaker magnet
• 1.5 T to 3 T – strength used in medical magnetic resonance imaging systems
• 4 T – strength of a special magnet at CERN
• 8 T – strength of LHC magnets
• 11.75 T – strength of the largest MRI scanner
• 13 T – strength of a big magnet system
• 14.5 T – strongest magnet for guiding particles at Fermilab
• 16 T – strength needed to lift a frog using water in its body
• 17.6 T – strongest field kept in a superconductor in a lab
• 20 T – strength of a big magnet for future energy experiments
• 27 T – strongest fields from very cold magnets
• 35.4 T – world record for a supercold magnet
• 45 T – world record for continuous magnetic fields
• 97.4 T – strongest field made without destroying the magnet
• 100 T – strength of a typical white dwarf star
• 1200 T – very short burst of magnetic field strength
• 10⁹ T – limit where magnetic fields change behavior
• 10⁸ – 10¹¹ T – magnetic strength of magnetar neutron stars

Notes and references

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