A student wraps a length of insulated wire into a coil around an iron rod and connects it to a battery. The student notices that the iron rod can now pick up steel paperclips. The student then increases the number of turns of wire on the coil. Explain why the iron rod behaves like a magnet, and describe two changes the student could make, other than increasing the number of turns, to make the electromagnet stronger.

The current flowing through the coil creates a magnetic field around each turn of wire. The fields from all the turns add together, giving a net field that is directed along the axis of the coil, just like a bar magnet. The iron rod placed in this field becomes magnetised – the magnetic domains in the iron align with the field, so the rod itself becomes an induced magnet. The combination of the coil’s field and the magnetised iron core gives a strong external field, allowing the rod to pick up paperclips.

To make the electromagnet stronger the student could:
1. Increase the current in the coil (e.g. by using a higher‑voltage battery or a lower‑resistance wire).
2. Use a core material with a higher magnetic permeability, such as soft iron or steel, instead of plain iron.

(Other options include increasing the coil length or the cross‑sectional area of the core.)