Magnetomotive Force Converter
Convert magnetomotive force between ampere-turns, kiloampere-turns, milliampere-turns, and gilberts. Enter an MMF value, then choose the units to convert from and to.
Convert Magnetomotive Force Between Units
Magnetomotive Force Conversion Formula
Where:
- \(F_{\mathrm{from}}\) — the entered magnetomotive force (MMF).
- \(F_{\mathrm{to}}\) — the MMF expressed in the selected destination unit.
- \(f_{\mathrm{from}}\) and \(f_{\mathrm{to}}\) — the conversion factors from each unit to ampere-turns (A·turn).
The calculator first expresses the entered value in ampere-turns, then divides by the destination unit’s factor. It uses factors of 1 for A·turn, 1,000 for kA·turn, 0.001 for mA·turn, and 0.7957747 for the gilbert.
Magnetomotive Force – Calculation Example
Example: convert the default value of 100 A·turn to gilberts (Gb).
\[100\ \mathrm{A\cdot turn}\times\frac{1}{0.7957747}\approx125.66371\ \mathrm{Gb}\]
Result: 100 A·turn is approximately 125.66371 Gb.
How to use the calculator
- Enter the amount to convert in MMF value. The default is 100, and the field accepts nonnegative values.
- Choose the unit of that amount under From unit. The default is Ampere-turn (A·turn).
- Choose the desired unit under To unit. The default is Gilbert (Gb).
- Read Converted MMF. The number and destination unit appear together.
You can also choose the same unit in both menus to leave the numerical value unchanged. To reverse a conversion, swap the selections in From unit and To unit.
What magnetomotive force means
Magnetomotive force is the quantity that drives magnetic flux around a magnetic circuit. It plays a role similar to voltage in an electric circuit, but it is not a mechanical force measured in newtons. In a coil, MMF is the current multiplied by the number of turns: \(\mathcal{F}=NI\), where \(N\) is the number of turns and \(I\) is the current in amperes. A 100-turn coil carrying 1 A therefore produces an MMF of 100 A·turn.
MMF is useful when analyzing transformers, electromagnets, motors, generators, and magnetic cores. It helps relate a winding’s excitation to the flux that may be established in a magnetic path. That relationship also depends on the path’s geometry and material: knowing MMF alone does not determine flux or flux density. For those quantities, use the Magnetic Flux converter or Magnetic Flux Density converter when you need to change their units.
A conversion changes only the unit used to express an MMF; it does not change the underlying excitation. Ampere-turn is the usual expression in SI-based magnetic calculations. The gilbert belongs to the CGS electromagnetic system and may appear in older references or specifications. Check the unit system of any equation before substituting a converted value.
Supported units and conversion factors
Each factor below states how many ampere-turns correspond to one unit. Multiply a value by its factor to express it in A·turn; divide an A·turn value by the factor to express it in that unit.
| Unit | Symbol | Value in A·turn |
|---|---|---|
| Ampere-turn | A·turn | 1 |
| Kiloampere-turn | kA·turn | 1,000 |
| Milliampere-turn | mA·turn | 0.001 |
| Gilbert | Gb | Approximately 0.7957747 |
For example, 1 kA·turn equals 1,000 A·turn, while 1 A·turn equals 1,000 mA·turn. The gilbert factor is approximate; using a more precise factor can produce a slightly different final decimal.
Assumptions and practical tips
The converter treats the number entered under MMF value as an already-known MMF. It does not calculate MMF from coil current and turns, nor does it account for the shape, length, or permeability of a magnetic path. If you start with a winding specification, calculate \(NI\) first; an Electric Current converter can help put the current in amperes.
The displayed result is rounded to eight decimal places. If you work with a very small value, check whether rounding hides significant digits before using the displayed number in a later calculation. For magnetic-circuit work, keep MMF distinct from magnetic flux, flux density, and permeability: they describe related but different properties and cannot be interchanged by a unit conversion.
Frequently Asked Questions
How do I find the current needed for a target magnetomotive force?
Divide the target MMF in ampere-turns by the number of coil turns: \(I=\mathcal{F}/N\). For example, a 250-turn coil needs 0.4 A to produce 100 A·turn. This gives the winding current, not a guarantee of a particular magnetic flux; the core and any air gap also matter.
What is a normal or good magnetomotive force value?
There is no universal good MMF value. The required excitation depends on the magnetic path, material, air gaps, and desired flux. A value suitable for a small sensor may be inadequate for an electromagnet. If you are designing a device, use its magnetic-circuit requirements and check practical limits such as winding heating and core saturation.
How is magnetomotive force related to magnetic field strength?
MMF is related to magnetic field strength \(H\) through Ampère’s law: \(\oint H\,\mathrm{d}l=NI\). If \(H\) is approximately uniform along a path of length \(l\), then \(H\approx NI/l\), in amperes per meter. In a core with an air gap, field strength generally differs between the core and gap, so dividing by one length can be misleading.
How do I calculate MMF when a core has more than one winding?
Add the windings’ ampere-turns with signs that reflect their directions: \(\mathcal{F}_{\mathrm{net}}=N_1I_1+N_2I_2+\cdots\). Windings that drive flux around the chosen path in opposite directions subtract. For example, 200 A·turn in one direction and 50 A·turn in the other give a net 150 A·turn. Establish a reference direction before assigning signs.
Can magnetomotive force be negative or vary with AC current?
Yes. A negative MMF indicates excitation opposite to a chosen reference direction; AC excitation changes magnitude and direction over time. For a coil, RMS current gives RMS MMF, while peak current gives peak MMF. Do not mix those values: for a sinusoid, peak MMF is \(\sqrt{2}\) times RMS MMF. This converter accepts nonnegative values, so convert the magnitude separately from its direction.
Are gilberts the same as gauss?
No. A gilbert measures magnetomotive force in the CGS system, whereas a gauss measures magnetic flux density. They cannot be converted directly because they describe different quantities. Also, the symbol “Gb” here means gilbert; check the quantity and surrounding unit system when reading older magnetic specifications to avoid confusing similarly abbreviated units.
Why might my gilbert conversion differ slightly from another source?
Different results often come from rounding the gilbert conversion factor. The more precise relationship is \(1\ \mathrm{Gb}=10/(4\pi)\ \mathrm{A\cdot turn}\), approximately 0.7957747155 A·turn. This calculator uses 0.7957747 and rounds its result to eight decimal places. Small differences are therefore expected, especially when converting large values or comparing many decimal places.
One thought on “Magnetomotive Force Converter”