Advanced Calculator
Choose the field source, select the unknown value, and enter positive values.
Formula Used
This calculator uses ideal magnetic field equations for common current sources.
- Long straight wire:
B = μI / (2πr)
- Circular loop center:
B = μNI / (2R)
- Long solenoid:
B = μNI / L
- Permeability:
μ = μ0 × μr
- Magnetic energy density:
u = B² / (2μ)
Here, B is magnetic flux density. I is current. r is wire distance.
R is loop radius. N is turns. L is solenoid length.
μ0 is the permeability of free space.
How to Use This Calculator
- Select a geometry type.
- Choose the value you want to solve.
- Enter current, target field, size, turns, and permeability.
- Select the correct units for each value.
- Press the calculate button.
- Review the result above the form.
- Use CSV or PDF buttons to export the result.
Example Data Table
| Case |
Geometry |
Current |
Turns |
Size |
Relative μ |
Approx Field |
| Phone wire check |
Straight wire |
5 A |
1 |
2 cm |
1 |
50 µT |
| Small lab coil |
Circular loop |
2 A |
80 |
8 cm |
1 |
1.26 mT |
| Air core solenoid |
Solenoid |
1.5 A |
400 |
25 cm |
1 |
3.02 mT |
| Iron assisted coil |
Solenoid |
0.8 A |
500 |
30 cm |
200 |
335 mT |
Understanding Magnetic Field and Current
A magnetic field appears around every moving electric charge. In circuits, the moving charges form current. That current creates a field around wires, loops, and coils. The field strength depends on current, shape, distance, turns, and material permeability.
Why Geometry Matters
A long straight wire spreads its field in circular paths. The field becomes weaker as distance increases. A circular loop concentrates the field near its center. More turns make the loop act like many loops working together. A solenoid creates a more uniform field inside its length. This makes solenoids useful in relays, sensors, speakers, motors, and laboratory coils.
Role of Permeability
Permeability shows how easily a material supports magnetic field formation. Air has a relative permeability near one. Iron and ferrite can have much higher values. A larger permeability can greatly increase the field for the same current. Real materials may saturate, so ideal equations are best for early design and study.
Using Results Carefully
The calculator gives values in tesla, millitesla, microtesla, and gauss. It also reports field intensity and energy density. These extra outputs help compare designs. For reference, Earth’s magnetic field is often near fifty microtesla. A result above that level can affect nearby compasses or sensitive sensors.
Practical Design Notes
Current creates heat in real conductors. Higher current may need thicker wire, insulation, and cooling. Coil resistance, core losses, nearby metals, and end effects can change actual readings. Measure final designs with a suitable meter when accuracy matters. Use this calculator for planning, learning, comparison, and quick engineering estimates.
FAQs
1. What does this calculator find?
It finds magnetic field, required current, distance, loop radius, or solenoid length. It supports straight wires, circular loops, and solenoids.
2. Which magnetic field unit should I use?
Use tesla for large fields. Use millitesla for coils. Use microtesla for weak fields. Use gauss for older magnetic references.
3. What is relative permeability?
Relative permeability compares a material with free space. Air is near one. Magnetic cores can be much higher, depending on material and saturation.
4. Are these results exact?
The results are ideal estimates. Real wires, short coils, core saturation, temperature, resistance, and nearby metal can change actual measurements.
5. Why do more turns increase the field?
Each turn adds magnetic effect. In an ideal coil or solenoid, the field is directly proportional to the number of turns.
6. Can I calculate current from a target field?
Yes. Select current as the unknown. Then enter the target magnetic field, geometry size, turns, and relative permeability.
7. Why does distance reduce wire field?
A straight wire field spreads outward in circles. As distance grows, the same magnetic influence covers a larger path.
8. What does the chart show?
The chart shows how magnetic field changes as current changes. It uses the selected geometry and calculated size values.