EMU of current to Biot
EMU
Bi
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 EMU (EMU of current) → 1 Bi (Biot) Just now · Rounding: Up to 8 significant figures | Recalculate this conversion using your current rounding settings. |
Quick Reference Table (EMU of current to Biot)
| EMU of current (EMU) | Biot (Bi) |
|---|---|
| 0.1 | 0.1 |
| 0.5 | 0.5 |
| 1 | 1 |
| 5 | 5 |
| 10 | 10 |
| 30 | 30 |
| 100 | 100 |
Results rounded to a maximum of 8 significant figures
About EMU of current (EMU)
The electromagnetic unit (EMU) of current is exactly identical to the biot within the CGS electromagnetic (CGS-EMU) system. Under the traditional pre-2019 CGS-to-SI mapping retained by this converter, one EMU of current corresponds to 10 amperes; that relationship is conventional rather than an exact physical conversion to the post-2019 SI. CGS-EMU dominated electrical physics from the mid-19th century until SI adoption in 1960. In CGS-EMU, the permeability of free space is defined as 1, giving the electromagnetic subsystem its characteristic form where magnetic force between parallel currents is expressed purely in dynes. The EMU of current appears in classical electrodynamics texts, historical measurement standards, and theoretical physics work using CGS-EMU conventions. All practical electrical measurement now uses SI amperes.
Under the traditional mapping used here, 1 EMU of current corresponds to 10 A. A 50 A arc welding process corresponds to 5 EMU. The unit is encountered primarily in pre-1960 scientific literature.
About Biot (Bi)
The biot (Bi) is the base unit of electric current in the centimeter-gram-second electromagnetic (CGS-EMU) system. Under the traditional pre-2019 CGS-to-SI mapping retained by this converter, one biot corresponds to 10 amperes. It is defined as the current in a pair of parallel conductors 1 cm apart that produces a force of 2 dynes per centimeter length — the CGS-EMU analogue of the former force-based SI ampere definition. The biot, EMU of current, and CGS e.m. unit are exactly the same current unit within CGS-EMU. Their 10 A relationship is a historical conversion convention rather than an exact physical conversion to the post-2019 SI, in which vacuum permeability is experimentally determined. The biot is essentially obsolete in modern practice, but it appears in older physics literature and classical electrodynamics textbooks alongside the dyne, gauss, and oersted.
Under the traditional mapping used here, 1 Bi corresponds to 10 A — roughly the draw of a domestic electric kettle. References to the biot appear primarily in historical or theoretical contexts, not modern instrumentation.
Etymology: Named after Jean-Baptiste Biot (1774–1862), French physicist who, with Félix Savart, established the Biot–Savart law describing the magnetic field generated by a steady electric current.
EMU of current – Frequently Asked Questions
What does EMU stand for and why was it created?
EMU stands for "electromagnetic unit." In the 1860s–1870s, physicists needed separate unit systems for electrostatic and electromagnetic phenomena because they had not yet unified them. The EMU system was built around magnetic force between currents, while the ESU system was built around Coulomb's electrostatic force. The ratio between them turned out to be the speed of light — a clue that led to Maxwell's equations.
Is the EMU of current the same as a biot?
Yes, exactly: the biot and EMU of current are two names for the same CGS-EMU unit. Under the traditional mapping used here, that unit corresponds to 10 amperes. The exact identity is between the two CGS names, not between the CGS unit and the post-2019 SI ampere. The CGS-EMU system also has named units for other quantities: the gauss (magnetic field), the oersted (magnetising field), and the maxwell (magnetic flux).
Why did physics abandon the EMU system?
The EMU system was awkward for practical electrical engineering — 1 EMU of resistance (the abohm) equals 10⁻⁹ ohms, making everyday values absurdly large numbers. The SI system, adopted in 1960, unified mechanical and electrical units into one coherent framework with human-scale values. Practicality won over tradition.
Where might I encounter EMU of current in old scientific papers?
Pre-1960 physics journals, particularly in geomagnetism, plasma physics, and early electrical standards work, routinely use EMU. Geophysicists measuring Earth's magnetic field historically reported results in CGS-EMU units (gauss, oersted, EMU). Some geophysics reference data still has not been converted to SI.
How did the speed of light connect the EMU and ESU systems?
Weber and Kohlrausch discovered in 1856 that the ratio of the ESU to EMU charge was approximately 3×10¹⁰ cm/s — the speed of light. This was no coincidence: Maxwell showed that light is an electromagnetic wave, and the unit ratio reflects the fundamental coupling between electric and magnetic fields. One of the greatest insights in physics history, hidden in a unit conversion.
Biot – Frequently Asked Questions
Why does this converter map one biot to 10 amperes?
The CGS-EMU system defines its base units using centimeters, grams, and seconds instead of meters, kilograms, and seconds. Under the former force-based SI ampere definition, converting the force between parallel currents made 1 Bi exactly 10 A. Since the 2019 SI redefinition, vacuum permeability is experimentally determined, so this converter retains 10 A as the stable traditional CGS-to-SI reference mapping rather than presenting it as an exact modern physical conversion.
Who was Jean-Baptiste Biot and why does he have a current unit?
Biot was a French physicist (1774–1862) who co-discovered the Biot–Savart law in 1820, describing how electric current generates a magnetic field in space. This was one of the foundational results linking electricity to magnetism. The CGS community honored him by naming their electromagnetic current unit after him.
Does anyone still use the biot in modern physics?
Essentially no. Even theorists who prefer CGS units typically use Gaussian units rather than pure CGS-EMU. The biot appears mainly in textbook conversion tables, historical physics papers, and graduate-level electrodynamics courses that teach multiple unit systems for pedagogical reasons.
How do I convert between biots and amperes?
Multiply biots by 10 to get amperes; divide amperes by 10 to get biots. A 30 A circuit carries 3 Bi; a 0.5 Bi current is 5 A. It is one of the simplest unit conversions in physics — just move the decimal point one place.
What is the Biot-Savart law and how does it relate to the biot unit?
The Biot-Savart law calculates the magnetic field produced by a small segment of current-carrying wire at any point in space. In CGS-EMU, it uses biots for current and gauss for the field. In SI it uses amperes and teslas. The law itself is fundamental — it is used to design MRI magnets, motors, and particle accelerators.