Grouping: Pairs or individual
Take-home: Electromagnet crane body + coil
Key ideas: Electric current creates a magnetic field; coil turns/core affect magnet strength; electricity can be switched on/off.
Start with: Connect a coil around an iron core briefly and pick up paper clips; disconnect it and release them.
Success check: Count standard paper clips lifted or complete a pick-up/drop-off task.
Try changing: Number of coil turns; core type; gap to load.
Preparation: Pre-cut equal wire lengths; prepare safe battery stations; build a known-good coil and crane mount.
CNC preparation: Useful: crane arm/base and switch panel.
3D-print preparation: Optional coil spool/strain relief.
Lesson flow: Day 1: build
Day 2: strength tests/redesign
Video:
How to Make an Electromagnet
Safety and cleanup: Use only low voltage; connect coils briefly because wire can warm; teacher controls batteries.
https://www.sciencebuddies.org/teacher-resources/lesson-plans/strength-of-electromagnet
https://www.youtube.com/watch?v=IyY4tYvyRmE