Build an electromagnet
Wind a coil around an iron nail, pass a current through it, and count how many paper clips it can lift as you change the turns, the current and the core.
Core concept
A coil carrying a current is a magnet; more turns, more current and an iron core make it stronger
Topic: Magnetism
A current: The flow of electricity through a wire, measured in amperes (A). All key words in a wire makes a magnet: An object that pulls iron and steel towards it. All key words field. Winding the wire into a coil (a solenoid) adds up the fields of all the turns, so the coil behaves like a bar magnet with N and S pole: One of the two ends of a magnet (north and south), where its pull is strongest. All key words. Putting a soft iron core inside makes the field hundreds of times stronger, because the iron becomes magnetised too. This is an electromagnet. Unlike a permanent magnet, it can be switched on and off and its strength can be changed by changing the current or the number of turns.
What you will learn
- Build an electromagnet and test its strength.
- Describe the effect of the number of turns, the current and the core.
- Give uses of electromagnets.
Before you start
- Know that a current-carrying wire has a magnetic field.
Materials
- Insulated copper wire, a large iron nail, a plastic straw and paper clips
Equipment
- Low-voltage power supply with an ammeter and a switch
Procedure
- With an iron core and 1 A, count the clips lifted with 20, 40 and 80 turns.
- With 40 turns, change the current to 0.5 A and 2 A.
- Replace the iron nail with a plastic straw (air core) and compare.
- Switch the current off and see what happens.
How this simulation is simplified
- Each paper clip needs the same pull; the field is proportional to turns × current.
- The soft iron core makes the field 20 times stronger than an air core.