A student sets up an electromagnet by wrapping a wire into a coil and connecting it to a battery. The student wants to make the electromagnet as strong as possible. Explain how the design of the electromagnet affects its magnetic field strength, and describe TWO changes the student could make to increase the strength of the magnetic field produced.

An electromagnet’s field is produced by the current in the coil and the magnetic permeability of the core. A coil of wire creates a magnetic field; the field strength is proportional to the current and to the number of turns, and the iron core provides a high‑permeability path that concentrates the field.

1. The iron core increases the field strength by providing a low‑reluctance path, so the field lines are concentrated compared with an air core.
2. The coil’s turns add their individual magnetic fields; the more turns, the greater the total field.
3. The magnetic field is also proportional to the current flowing through the coil.

Two changes that will increase the field:
• Increase the current (e.g. use a higher‑voltage battery or a lower‑resistance wire).
• Increase the number of turns (e.g. wind more turns of wire around the core).