4PH1
Magnetism & Electromagnetism
Magnetism & Electromagnetism · 1 question type
Exam Frequency Analysis
Past paper frequency (2018 to 2024)
This topic accounts for approximately 9% of your exam marks.
stable
Medium
Stable9%
Magnetic field patterns, the motor effect and Fleming's Left-Hand Rule tested in most series.
Permanent magnets
- A permanent magnet is made from a magnetically hard material (like steel or a special rare-earth alloy)
- It produces its own magnetic field and keeps doing so even when no other magnet is nearby
- A permanent magnet does not need a current to work
Induced magnets
- An induced magnet is a piece of that has been temporarily turned into a magnet by sitting in another magnet's field
- The end of the induced magnet closest to the inducing magnet's pole takes the opposite sign (so the two are attracted)
- The induced magnetism is lost almost as soon as the original magnet is removed, so soft iron releases its magnetism within a fraction of a second
- Induced magnetism is why a paperclip will hang from a bar magnet, and a second paperclip can then hang from the first one, and so on, forming a short chain. Each clip is briefly magnetised by the one above it
