🧲 Electromagnet (2D)

This 2D companion drives the same B = μ·n·I solenoid formula as the 3D version through a flat side-view canvas: an iron or air core sits inside a wound coil, current-direction chevrons ride the coil, field-line loops arc from the north to the south pole, and a row of compass needles above and below the coil rotate to track the local field as you change current, turns or polarity.