Electromagnetism — AQA GCSE Physics
Test yourself on Electromagnetism with AQA GCSE practice questions.
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Electromagnetism explained
Slide an iron core inside a solenoid and the magnetic field gets much stronger for the same current.
Read the full explanation
The core sits in the coil's field and becomes an induced magnet, so its own field adds to the coil's and the total field outside is far greater. Take the core out and the field is weaker again. Iron is the required material because it is magnetically soft: it is easily magnetised and easily demagnetised. This means it strengthens the field while the current flows and loses its magnetism the moment the current stops. Steel is rejected because it is magnetically hard and keeps its magnetism, leaving the electromagnet permanently on.
Your focus
- Predict how the strength of an electromagnet's field changes when its metal core is removed and the current is kept the same.
- Justify the choice of iron rather than steel for the core of an electromagnet.
- Explain in terms of induced magnetism why the core strengthens the field.
Electromagnetism exam tips
Marking Points
- stating that adding an iron core increases the strength of the magnetic field
- stating that removing the core makes the field weaker at the same current
- explaining that the core becomes an induced magnet so its field adds to that of the coil
- justifying iron as the material because it is easily magnetised and demagnetised
Examiner Tips
- 💡Core questions want the specific material (iron) and the reason; the reason mark usually depends on the material mark.
- 💡Write both halves of the reason: easily magnetised and easily demagnetised.
Common Mistakes
- saying the core increases the current in the coil, rather than increasing the magnetic field strength
- choosing steel, nickel, or cobalt for the core; AQA specifically requires iron for electromagnets
- claiming the core stores the magnetism so the electromagnet stays on after the current stops, instead of demagnetising
- giving only 'easily magnetised' and leaving out 'and easily demagnetised' when explaining the choice of iron