ESU of current to Weber per henry
ESU
Wb/H
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
| No conversion history to show. | ||
Quick Reference Table (ESU of current to Weber per henry)
| ESU of current (ESU) | Weber per henry (Wb/H) |
|---|---|
| 1 | 0.0000000003335641 |
| 10 | 0.000000003335641 |
| 100 | 0.00000003335641 |
| 1,000,000 | 0.0003335641 |
| 1,000,000,000 | 0.3335641 |
| 3,000,000,000 | 1.0006923 |
Results rounded to a maximum of 8 significant figures
About ESU of current (ESU)
The electrostatic unit of current (ESU, also called the statampere) equals approximately 3.335640952×10⁻¹⁰ amperes under the traditional CGS-to-SI mapping used by this converter. It is the current unit of the CGS electrostatic system (CGS-ESU), in which Coulomb's law is written without a permittivity constant and electric charge is measured in statcoulombs (franklins). One statampere is the flow of one statcoulomb per second. The traditional mapping is 1 A = (c/10) statamperes, using the numerical speed of light c = 29,979,245,800 in cm/s, so 1 A maps to 2,997,924,580 statamperes. This is a conventional mapping, not a claim of an exact physical conversion to the post-2019 SI. The CGS-ESU system was used in early electrostatics and vacuum tube physics but is obsolete in applied engineering.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 Weber per henry (Wb/H)
The weber per henry (Wb/H) equals one ampere, derived from inductance: the magnetic flux Φ stored in an inductor equals inductance L times current I (Φ = L·I), so I = Φ/L = Wb/H. This form appears in electromagnetic field theory and inductor design where engineers compute the current required to establish a given magnetic flux in a core. One weber of flux in a one-henry inductor corresponds to exactly one ampere of magnetising current. The Wb/H notation is common in transformer and motor design calculations, magnetic circuit analysis, and advanced EMC engineering where field and circuit quantities must be reconciled.
A 1 H inductor carrying 5 A stores 5 Wb of magnetic flux — expressed as 5 Wb/H. Power transformer core saturation analysis links flux density to Wb/H magnetising current.
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. 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.
What is a statampere and is it the same as an ESU of current?
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."
Did the 2019 SI redefinition change the statampere?
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.
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.
Weber per henry – Frequently Asked Questions
Why would a transformer designer think in webers per henry?
When designing a transformer, you start with the required flux (webers) to transfer power at a given voltage and frequency. The core's inductance (henries) is set by geometry and material. Dividing flux by inductance gives the magnetising current that must flow — and if it is too high, the core saturates and the transformer overheats.
What is a weber in practical terms?
One weber is the magnetic flux that, when reduced to zero in one second, induces one volt in a single-turn coil. A small transformer core might carry 0.001 Wb (1 mWb) of peak flux. The Earth's magnetic field through a 1 m² loop is about 50 μWb. One weber is actually an enormous amount of flux in everyday terms.
What happens when the Wb/H calculation shows too much current?
If the calculated magnetising current (Wb/H) exceeds design limits, the core is approaching magnetic saturation. The inductance drops sharply, current spikes further, and the inductor or transformer overheats. Solutions include using a larger core, higher-permeability material, an air gap, or reducing the operating flux density.
How does core saturation relate to the Wb/H ratio?
Every magnetic core has a saturation flux density (e.g., 1.5 T for silicon steel, 0.3 T for ferrite). When flux approaches this limit, permeability collapses, inductance plummets, and Wb/H (current) shoots up. Power supply designers must ensure peak flux stays 20–30% below saturation under worst-case conditions.
How does an air gap in an inductor core change the Wb/H calculation?
An air gap dramatically increases the reluctance of the magnetic circuit, which lowers inductance (H) for the same core geometry. For a given flux (Wb), the magnetising current (Wb/H) increases — but the core is far harder to saturate. Power supply designers deliberately add 0.1–1 mm air gaps to ferrite cores so the inductor can handle higher peak currents without the flux density hitting saturation limits.