Knowledge Organiser: Magnetic Fields and Electromagnets
Part of Magnetic Fields · GCSE GCSE Physics revision
This topic summary covers Knowledge Organiser: Magnetic Fields and Electromagnets within Magnetic Fields for GCSE Physics. Revise Magnetic Fields in Magnetism for GCSE Physics with 13 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 15 of 15 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 15 of 15
Practice
13 questions
Recall
12 flashcards
Knowledge Organiser: Magnetic Fields and Electromagnets
Key Terms
- Magnetic field: region where magnetic material feels a force
- Permanent magnet: always magnetic (steel)
- Induced magnet: temporarily magnetic (iron)
- Electromagnet: current in coil creates magnetic field
- Magnetic flux density (B): field strength in Tesla (T)
Key Facts
- Field lines: N to S outside, arrows, closer = stronger, never cross
- Like poles repel; unlike poles attract
- Induced magnets ALWAYS attract to permanent magnets
- Soft iron core: loses magnetism when current stops
- Steel core: retains magnetism (hard magnetic material)
Electromagnet Strength
- Increase current (I)
- Increase number of turns/coils
- Add soft iron core
- Uses: cranes, MRI, relays, bells, loudspeakers
Exam Tips
- Always add arrows to field lines (N to S outside)
- Iron core NOT steel — must be able to switch off
- Induced magnets cannot be repelled
- Cutting a magnet makes two smaller magnets (no monopoles)
Key Equations
- Closer field lines = stronger magnetic field
- Electromagnet strength ∝ current × number of turns
- Field direction: right-hand rule for a solenoid (thumb = N pole direction)
- Magnetic force on a conductor: F = B × I × L (Higher tier)
Common Mistakes
- Drawing field lines without arrows: Magnetic field lines must have arrows showing direction from North to South pole outside the magnet — missing arrows loses marks
- Using steel instead of iron for electromagnet cores: Iron is used because it is a temporary (soft) magnetic material — it magnetises and demagnetises easily; steel retains magnetism and cannot be switched off
- Saying induced magnets can be repelled: Induced magnets always have the opposite pole facing the permanent magnet — they are always attracted, never repelled
- Confusing permanent and induced magnets: Permanent magnets retain their magnetism; induced magnets only become magnetic when near a magnet and lose it when removed
- Thinking cutting a magnet removes a pole: Cutting a bar magnet creates two complete magnets each with a North and South pole — isolated magnetic monopoles do not exist
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Practice Questions for Magnetic Fields
What happens when two like magnetic poles (e.g. north and north) are brought close together?
State the rules for the attraction and repulsion of magnetic poles.
Quick Recall Flashcards
13 questions on Magnetic Fields — practise free
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