Gilbert to Gaussian electric current
Gi
G cgs
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
1 Gi (Gilbert) → 2385673434.066683846674148974284491 G cgs (Gaussian electric current) Just now |
Quick Reference Table (Gilbert to Gaussian electric current)
| Gilbert (Gi) | Gaussian electric current (G cgs) |
|---|---|
| 0.1 | 238,567,343.40666838467041282201023 |
| 0.5 | 1,192,836,717.033341923322084864233341 |
| 1 | 2,385,673,434.066683846674148974284491 |
| 2 | 4,771,346,868.133367693348297948568982 |
| 5 | 11,928,367,170.333419233340765625604646 |
| 10 | 23,856,734,340.666838466681531251209292 |
| 100 | 238,567,343,406.668384666725374774639493 |
About Gilbert (Gi)
The gilbert (Gi) equals 10/(4π) amperes — approximately 0.7958 A — and is the CGS-EMU unit of magnetomotive force (MMF) rather than a general-purpose current unit. In magnetic circuit analysis, MMF drives magnetic flux through a reluctance, analogously to how voltage drives current through resistance. A single-turn coil carrying 1 Gi of MMF passes 0.7958 A. In SI, magnetomotive force is measured in ampere-turns (A·T). The gilbert is obsolete but historically significant in transformer design, relay engineering, and magnetic circuit analysis dating from the late 19th century through the 1960s.
A relay coil requiring 2 Gi of MMF to actuate needs about 1.6 A·turn in SI terms. Vintage transformer and relay datasheets from the 1940s–1960s often specify MMF in gilberts.
Etymology: Named after William Gilbert (1544–1603), English physician and natural philosopher who authored De Magnete (1600), the first systematic scientific study of magnetism and electricity, establishing that the Earth itself acts as a giant magnet.
About Gaussian electric current (G cgs)
The Gaussian unit of electric current equals approximately 3.335641×10⁻¹⁰ amperes, derived from the Gaussian CGS system in which the speed of light c enters electromagnetic relations explicitly rather than through permittivity or permeability constants. One Gaussian current unit equals one statampere — one statcoulomb per second — and the SI conversion is I_SI = I_Gaussian × c_cm/s / 10, where c ≈ 2.998×10¹⁰ cm/s. The Gaussian system remains common in theoretical and computational physics, plasma physics, quantum electrodynamics, and astrophysics literature where its symmetric treatment of electric and magnetic fields simplifies equations.
1 Gaussian current unit ≈ 3.336×10⁻¹⁰ A. Plasma physics and astrophysics papers routinely quote electromagnetic quantities in Gaussian units rather than SI.
Gilbert – Frequently Asked Questions
Why is the gilbert approximately 0.7958 amperes and not a round number?
The gilbert equals 10/(4π) amperes because the CGS-EMU system uses a different form of Ampere's law where the factor 4π appears explicitly rather than being absorbed into μ₀. This "unrationalised" form distributes 4π differently in the equations, producing the 1/(4π) factor when converting to SI's "rationalised" system.
What is magnetomotive force and how is it different from regular current?
MMF is the magnetic analogue of voltage — it drives flux through a magnetic circuit the way EMF drives current through an electrical circuit. For a coil, MMF = N × I (turns times current). A 100-turn coil carrying 1 A has 100 ampere-turns of MMF. In CGS, that same MMF would be about 125.7 gilberts.
Who was William Gilbert and why does he deserve a unit?
Gilbert (1544–1603) was physician to Queen Elizabeth I and author of De Magnete (1600), the first true scientific investigation of magnetism. He demonstrated that Earth is a magnet, distinguished magnetic from electrostatic attraction, and coined the word "electricus." He did all this 87 years before Newton's Principia — a genuine pioneer of experimental science.
Where would I find gilberts used today?
Practically nowhere in new designs. You might encounter gilberts in vintage relay and transformer datasheets from the 1940s–1960s, in older American and European magnetic component catalogs, or in classic electrical engineering textbooks. Any modern magnetic circuit analysis uses ampere-turns (A·T) for MMF.
How do I convert gilberts to ampere-turns?
Multiply gilberts by 10/(4π) ≈ 0.7958 to get ampere-turns. Wait — that is backwards. Multiply gilberts by 0.7958 to get amperes for a single-turn coil. For MMF conversion: 1 gilbert = 0.7958 ampere-turns. So a relay spec of 5 Gi needs about 4 ampere-turns to actuate — for instance, 4 turns at 1 A or 8 turns at 0.5 A.
Gaussian electric current – Frequently Asked Questions
Why do astrophysicists prefer Gaussian units over SI?
In Gaussian units, electric and magnetic fields have the same dimensions, and Maxwell's equations look more symmetric — no ε₀ or μ₀ cluttering the formulas. When you study electromagnetic radiation in vacuum (starlight, cosmic rays, pulsar emissions), this symmetry is physically meaningful and simplifies calculations considerably.
What makes Gaussian CGS different from pure ESU or EMU?
Gaussian is a hybrid: it uses ESU conventions for electric quantities (charge, electric field, current) and EMU conventions for magnetic quantities (magnetic field, flux). This cherry-picking gives clean equations for both electrostatic and magnetic phenomena, at the cost of the speed of light appearing explicitly in equations linking electric and magnetic fields.
What happens to the fine-structure constant when you switch from SI to Gaussian units?
In SI, the fine-structure constant α = e²/(4πε₀ℏc) ≈ 1/137. In Gaussian units, ε₀ disappears and α simplifies to e²/(ℏc) — cleaner and more physically transparent. This is one reason particle physicists and quantum electrodynamics theorists favor Gaussian: fundamental constants combine more naturally, and the coupling strength of electromagnetism is immediately visible as α ≈ 1/137.
How do Gaussian units make Maxwell's equations look more elegant?
In Gaussian CGS, Maxwell's equations replace ε₀ and μ₀ with explicit factors of c, and the electric field E and magnetic field B end up with the same dimensions. The symmetric form ∇×E = −(1/c)∂B/∂t and ∇×B = (1/c)∂E/∂t reveals that E and B are equal partners in electromagnetic waves — a physical insight that SI's asymmetric constants obscure.
Why does Jackson's Classical Electrodynamics textbook use Gaussian units?
J.D. Jackson chose Gaussian units because they reveal the deep symmetry between electric and magnetic fields and make relativistic electrodynamics equations cleaner. His textbook, used in virtually every physics PhD program since 1962, cemented Gaussian as the "language" of theoretical electromagnetism. Later editions added SI appendices as a concession to modernity.