It’s an electromagnet pendulum analog circuit. Whether you’re building it, or just studying the schematics, this is a fun way to brush up on the non-digital side of the craft. The pendulum is ...

Iron and steel make strong electromagnets. The current increases. The number of turns in the coil increases. An iron core makes a strong electromagnet which can be easily magnetised and demagnetised.

Remember - these variables are controlled (or kept the same) because to make it a fair test ... the magnetic field and hence the stronger the electromagnet. Hazard Consequence Control measures ...