Biot to CGS e.s. unit
Bi
CGS ESU
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 Bi (Biot) → 29979245368.43143491760654099167 CGS ESU (CGS e.s. unit) Just now |
Quick Reference Table (Biot to CGS e.s. unit)
| Biot (Bi) | CGS e.s. unit (CGS ESU) |
|---|---|
| 0.1 | 2,997,924,536.84314349176065409917 |
| 0.5 | 14,989,622,684.21571745880327049584 |
| 1 | 29,979,245,368.43143491760654099167 |
| 5 | 149,896,226,842.15717458803270495836 |
| 10 | 299,792,453,684.31434917606540991671 |
| 30 | 899,377,361,052.94304752819622975014 |
| 100 | 2,997,924,536,843.14349176065409916715 |
About Biot (Bi)
The biot (Bi) equals exactly 10 amperes and is the base unit of electric current in the centimeter-gram-second electromagnetic (CGS-EMU) system. 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 SI ampere definition. In the CGS-EMU system the biot plays the same foundational role the ampere plays in SI: all other electromagnetic CGS-EMU units are derived from it. 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.
A current of 1 Bi equals 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.
About CGS e.s. unit (CGS ESU)
The CGS electrostatic unit (CGS e.s. unit) of current equals approximately 3.335641×10⁻¹⁰ amperes, identical to the statampere or ESU of current. In the CGS electrostatic subsystem, current is defined as statcoulombs per second, giving one CGS e.s. unit per second of charge flow. The CGS-ESU system places Coulomb s law in a clean constant-free form but produces cumbersome dimensions for magnetic quantities. It was used in early electrostatics, cathode-ray tube physics, and vacuum science. All modern work uses SI. The factor 1/c (in CGS cm/s) converts ESU current to SI amperes.
1 CGS e.s. unit ≈ 3.336×10⁻¹⁰ A. A 1 A current equals about 3×10⁹ CGS e.s. units — illustrating the enormous scale difference between the ESU and SI systems.
Biot – Frequently Asked Questions
Why is the biot exactly 10 amperes and not some other factor?
The CGS-EMU system defines its base units using centimeters, grams, and seconds instead of meters, kilograms, and seconds. The factor of 10 falls out naturally from the dimensional conversion: 1 Bi produces 2 dyn/cm force between wires 1 cm apart, and working through the CGS-to-SI conversion yields exactly 10 A.
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.
CGS e.s. unit – Frequently Asked Questions
Why is the CGS e.s. unit so different in magnitude from the CGS e.m. unit?
The e.m. unit equals 10 A while the e.s. unit equals 3.3 × 10⁻¹⁰ A — a ratio of about 3 × 10¹⁰, which is the speed of light in cm/s. This enormous factor reflects the fundamental relationship c² = 1/(ε₀μ₀). The two systems were designed to simplify different sets of equations, and the speed of light is the price of bridging them.
What made the CGS electrostatic system useful for early vacuum physics?
In vacuum tubes and cathode ray experiments, electrostatic forces dominate — no magnetic materials, no currents in bulk conductors. The ESU system made Coulomb's law beautifully simple: F = q₁q₂/r² with no constants. For computing electron trajectories in early TV tubes and oscilloscopes, this simplicity was genuinely helpful.
How did early CRT televisions use electrostatic units in beam deflection design?
Early cathode ray tubes used electrostatic deflection plates to steer the electron beam. Engineers working in CGS-ESU could calculate beam deflection angles directly from plate voltage and geometry using Coulomb's law without extra constants. The tiny ESU currents matched the actual beam currents (microamperes), making the numbers more intuitive than working in amperes for these minuscule electron flows.
How do I know if an old paper is using CGS e.s. or CGS e.m. units?
Check the context and the magnitude of numbers. If currents are tiny numbers where you would expect amperes, it is ESU. If they are 1/10 of expected ampere values, it is EMU. Good papers state which system they use, but many older ones do not. The equations themselves also differ — look for factors of c or 4π.
Could the CGS electrostatic system handle magnetic phenomena?
Technically yes, but clumsily. In pure CGS-ESU, the magnetic field has dimensions involving the speed of light, and equations for inductance and magnetic force become awkward. This is exactly why the Gaussian hybrid was invented — it uses ESU for electric quantities and EMU for magnetic ones, giving clean equations for both.