Currents Make Fields

Electromagnets

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Currents produce magnetic fields (Ørsted, 1820).
• Around a straight wire the field forms circles, with $B \propto I/r$ (right-hand rule).
• Coils (solenoids) with iron cores make strong, switchable electromagnets.

Steps

1. Ørsted’s surprise
2. Circles around a wire
3. Stronger electromagnet
4. Field near a wire
5. Fooling a compass
6. Farther away