Milliampere to Biot
mA
Bi
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 mA (Milliampere) → 0.0001 Bi (Biot) Just now · Rounding: Up to 8 significant figures | Recalculate this conversion using your current rounding settings. |
Quick Reference Table (Milliampere to Biot)
| Milliampere (mA) | Biot (Bi) |
|---|---|
| 1 | 0.0001 |
| 5 | 0.0005 |
| 20 | 0.002 |
| 100 | 0.01 |
| 500 | 0.05 |
| 1,000 | 0.1 |
| 2,000 | 0.2 |
Results rounded to a maximum of 8 significant figures
About Milliampere (mA)
The milliampere (mA) equals one thousandth of an ampere (10⁻³ A) and is the practical unit for most consumer electronics and lighting circuits. USB 2.0 ports supply up to 500 mA; USB-C Power Delivery can reach 5,000 mA (5 A). A standard 5 mm indicator LED operates at 10–20 mA; mid-power LED drivers supply 100–350 mA. Human perception of electric shock begins near 1 mA; currents above 10 mA cause involuntary muscle contraction, and above 100 mA can be lethal. Wireless sensors, earphones, and small motors typically draw single-digit to low-hundreds of milliamperes.
A USB 2.0 port provides up to 500 mA for charging. A standard 5 mm indicator LED operates at around 20 mA.
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.
Milliampere – Frequently Asked Questions
How many milliamps is dangerous to a human?
The danger thresholds for 50/60 Hz AC are roughly: 1 mA (tingling), 10–20 mA (muscle lock — you cannot let go), 75–100 mA (ventricular fibrillation), and 200+ mA (cardiac arrest and burns). DC is somewhat less dangerous at the same current. Duration matters enormously — 100 mA for 1 second is more lethal than 100 mA for 10 ms.
Why is my phone charger rated in milliamps when it charges at 2 amps?
Battery capacity is rated in milliampere-hours (mAh), not milliamps. A 4,000 mAh battery holds 4,000 mA for one hour (or 2,000 mA for two hours). The charger delivers 2 A (2,000 mA) of current, and it takes about 2 hours to fill that 4,000 mAh battery from empty.
What is the milliamp draw of common household items?
A wireless earbud draws 5–15 mA during playback. A TV remote uses about 10 mA when pressing a button. An LED nightlight consumes 20–50 mA. A smoke detector in standby draws 10–30 μA (0.01–0.03 mA) — so low it runs on a 9V battery for years.
Why do LED specifications always mention 20 mA?
Standard 5 mm indicator LEDs were designed around a 20 mA operating point — bright enough to see clearly, low enough to avoid overheating the tiny die. All datasheet specs (luminous intensity, color, forward voltage) are measured at this "test current." High-power LEDs use 350 mA or 700 mA as their reference instead.
How does milliamp-hour (mAh) relate to milliamp (mA)?
Milliamp-hours measure charge capacity; milliamps measure current flow rate. A 2,000 mAh battery can deliver 2,000 mA for 1 hour, or 200 mA for 10 hours, or 20 mA for 100 hours — current times time equals capacity. Dividing mAh by mA gives approximate runtime in hours.
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.