ESU of current to Milliampere

The ESU system was designed to make Coulomb's electrostatic law simple (no constants), which means its charge unit (the statcoulomb) is tiny relative to the coulomb. Since current is charge per time, the statampere inherits that smallness. Under the traditional mapping used here, one ampere maps to 2,997,924,580 statamperes — the numerical speed of light in cm/s divided by 10. In the reverse direction, multiply the statampere value by 10/c, or divide by 2,997,924,580, to obtain amperes.

Yes. Statampere, ESU of current, CGS electrostatic current, franklin per second and Gaussian current share the same current scale. This converter uses the same traditional mapping for all five names: 1 A maps to 2,997,924,580 statamperes. "Statampere" is the named form; "ESU of current" is the descriptive form. The "stat-" prefix comes from "electrostatic," just as the "ab-" prefix in the EMU system comes from "absolute."

No. The statampere remains one statcoulomb per second in the CGS system. What changed was the SI ampere: in 2019 it was redefined by fixing the elementary charge, replacing its earlier force-based definition. Vacuum permeability and permittivity are consequently no longer exact SI constants, so physical conversions between CGS electrical units and modern SI involve measured values and uncertainty. This converter retains the pre-2019 mapping of 1 A to 2,997,924,580 statamperes for consistent reference conversions; it does not apply modern measured corrections.

When Weber and Kohlrausch measured the ratio of ESU to EMU charge in 1856, they got a number suspiciously close to the speed of light — about 3×10¹⁰ cm/s. Maxwell realized this was no coincidence: it meant electromagnetic disturbances propagate at light speed, proving light itself is an electromagnetic wave. A unit conversion exercise led to one of the greatest discoveries in physics.

Telegraph cables behaved like long capacitors — charge stored along the line distorted signals over transatlantic distances. The ESU system, built around Coulomb's law, made capacitance calculations straightforward: no permittivity constants, just geometry and charge. William Thomson (Lord Kelvin) used ESU-based analysis to diagnose and fix signal distortion on the first transatlantic telegraph cables in the 1860s.

Electrostatic experiments (rubbing rods, Leyden jars, spark gaps) involved high voltages and tiny charges, while electromagnetic work (coils, galvanometers, telegraph lines) involved low voltages and large currents. The equipment, techniques, and even the physicists were different. Each community built units natural to their measurements — ESU for electrostatics, EMU for electromagnetics — and it took decades after Maxwell to unify them into one coherent SI framework.

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.

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.

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.

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.

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.