Kiloampere to Gilbert
kA
Gi
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
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Quick Reference Table (Kiloampere to Gilbert)
| Kiloampere (kA) | Gilbert (Gi) |
|---|---|
| 1 | 1,256.6366121077 |
| 10 | 12,566.366121077 |
| 30 | 37,699.098363231 |
| 100 | 125,663.66121077 |
| 200 | 251,327.32242154 |
| 300 | 376,990.98363231 |
About Kiloampere (kA)
The kiloampere (kA) equals one thousand amperes and appears where extremely high currents are generated or measured. A typical lightning bolt carries a peak current of 20–30 kA, though extreme strokes can exceed 200 kA. Industrial arc furnaces melting steel draw 50–100 kA through graphite electrodes. Aluminum electrolysis cells in smelters operate at 150–500 kA of continuous DC current per pot. Rail electromagnetic launchers pulse at hundreds of kiloamperes. Resistance spot welding uses 5–30 kA pulses lasting milliseconds to join metal sheets.
A typical lightning bolt peaks at 20–30 kA. Aluminum smelting cells run continuously at 150–300 kA of electrolysis current.
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 The gilbert is obsolete but historically significant in transformer design, relay engineering, and magnetic circuit analysis dating from the late 19th century through the 1960s.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.
Kiloampere – Frequently Asked Questions
How does a spot welder push 10,000 amps through two sheets of metal?
A spot welder uses a large step-down transformer: high voltage at low current on the primary becomes very low voltage (1–2 V) at enormous current (5–30 kA) on the secondary. The copper electrode tips concentrate this current into a small spot, melting the metal in milliseconds. Total power is only 10–60 kW — it is the concentration that does the work.
What happens to a wire if you put a kiloampere through it?
A typical 14 AWG house wire rated for 15 A would vaporise almost instantly at 1 kA — the I²R heating would melt copper in milliseconds. Industrial busbars carrying kiloamperes are massive rectangular copper or aluminum bars, sometimes water-cooled, with cross-sections of 10–100 cm² to keep current density manageable.
How much current does a lightning bolt actually carry?
A typical negative cloud-to-ground stroke peaks at 20–30 kA for about 1–2 microseconds. Positive lightning (rarer, about 5% of strikes) can exceed 300 kA. The total charge transferred is only 1–5 coulombs because the pulse is so brief — enormous current, tiny duration.
Why do aluminum smelters need hundreds of kiloamperes?
Aluminum oxide dissolved in molten cryolite at 960 degrees C requires direct electrolytic reduction to separate aluminum metal. Each smelting pot runs at 4–5 V but needs 150–500 kA because the electrochemical reaction requires massive charge transfer. A single smelter may consume 1–2 GW — as much as a small city.
What protects electrical systems from kiloampere fault currents?
Circuit breakers rated for 10–200 kA interrupting capacity use arc-quenching chambers to extinguish the plasma arc that forms when contacts open under fault current. High-rupture-capacity (HRC) fuses have sand-filled ceramic bodies that absorb the arc energy. Without these devices, a short circuit on a utility feed would weld everything in the panel into slag.
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.