Designed and built a small electromagnetic car for AP Physics C in high school. The car used two AA batteries wired in a parallel circuit to power both a set of drive wheels and a homemade electromagnet at the same time. The electromagnet was built by wrapping copper wire around a bolt to create a coil that could generate a magnetic field strong enough to pick up metal objects. The goal was to drive the car to a set of paper clips and pick up all 10 of them.
The main challenge was figuring out how to power two separate systems, the motors and the electromagnet, from the same low-voltage battery source without one system pulling too much current and weakening the other. A series circuit would have split the voltage and left both systems underpowered, so the wiring setup needed to be thought through carefully.
Started by planning out the circuit on paper before building anything. Chose a parallel configuration so both the drive motors and the electromagnet would each receive the full 1.5 volts from the batteries rather than sharing it. The AP Physics C coursework on electromagnetism and Ampere's Law directly informed the decision to maximize the number of wire turns on the bolt, since more turns means a stronger magnetic field.
Getting the electromagnet strong enough to reliably lift paper clips took several winding attempts. Too few turns and the magnet was too weak. The parallel circuit also needed to be wired cleanly to avoid shorts, which required careful attention during assembly. Balancing the car's weight distribution so it could drive straight while carrying the electromagnet on the front also took some adjustment.
The car successfully picked up all 10 paper clips in the final test. The parallel circuit kept both systems running at full power throughout the run, and the hand-wound electromagnet held all 10 clips without dropping any.
This project brought a lot of the AP Physics C curriculum to life in a hands-on way. Concepts like magnetic flux, current loops, and circuit analysis stopped being just formulas and became real design decisions with visible results. Planning the circuit layout before starting the physical build also saved a lot of time and prevented wiring mistakes during assembly.