Solenoid Magnetic Field
Visualize the magnetic field of a solenoid — a helical coil of wire. The field lines run straight through the interior and loop around the exterior.
Field lines (B)
Current out (⊙)
Current in (⊗)
Biot-Savart law: Each infinitesimal current element dI contributes dB = μ₀I(dL×r̂)/4πr².
For an ideal infinite solenoid, B = μ₀nI inside (uniform, axial) and B≈0 outside.
A finite solenoid has fringe fields at the ends. The field here is computed numerically by summing contributions
from each discrete loop of the coil.