ESU of current to CGS e.s. unit
ESU
CGS ESU
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 ESU (ESU of current) → 1 CGS ESU (CGS e.s. unit) Just now |
Quick Reference Table (ESU of current to CGS e.s. unit)
| ESU of current (ESU) | CGS e.s. unit (CGS ESU) |
|---|---|
| 1 | 1 |
| 10 | 10 |
| 100 | 100 |
| 1,000,000 | 1,000,000 |
| 1,000,000,000 | 1,000,000,000 |
| 3,000,000,000 | 3,000,000,000 |
About ESU of current (ESU)
The electrostatic unit of current (ESU, also called the statampere) equals approximately 3.335641×10⁻¹⁰ amperes. It is the current unit of the CGS electrostatic system (CGS-ESU), in which Coulomb s law is written without a permittivity constant and electromagnetic quantities are derived from the statcoulomb (franklin). One statampere is the flow of one statcoulomb per second. The factor 3.336×10⁻¹⁰ arises because 1 A = (c/10) ESU, where c ≈ 3×10¹⁰ cm/s is the speed of light in CGS units. The CGS-ESU system was used in early electrostatics and vacuum tube physics but is entirely obsolete in applied engineering.
1 ESU of current ≈ 3.336×10⁻¹⁰ A — an extraordinarily small current. One ordinary ampere equals approximately 3×10⁹ ESU.
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.
ESU of current – Frequently Asked Questions
Why is the ESU of current so absurdly small compared to an ampere?
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. One ampere is about 3 billion statamperes — the speed of light (in cm/s) divided by 10 shows up in the conversion.
What is a statampere and is it the same as an ESU of current?
Yes, the statampere and the ESU of current are exactly the same unit: approximately 3.336 × 10⁻¹⁰ A. "Statampere" is the named form; "ESU of current" is the descriptive form. The "stat-" prefix comes from "electrostatic," just as "ab-" prefix in the EMU system comes from "absolute."
What role did the ESU system play in the discovery that light is electromagnetic?
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.
What practical problem did the ESU system solve for 19th-century telegraph engineers?
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.
Why were electrostatic and electromagnetic measurements historically done in separate labs?
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.
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.