Document page
igcse physics notesprinted 94 · PDF 94
124 pagesrevision 46936
printed 94 · PDF 94
Page image rendered from the stored file at 110 dpi; it sharpens as you zoom. Outlines are placed from each region’s stored position on the page (612 × 792 pt).
readable
Source of this text: embedded text layer. The better of the embedded text and OCR is kept.
94
UNIT 4: MAGNETISM AND ELECTRICITY
Simple phenomena of magnetism
Magnetic forces are due to interactions between magnetic fields. In a
magnet, like poles repel
and opposite poles attract.
● Magnetic materials are materials that are attracted to magnets and can
be magnetized (e.g. iron, steel, cobalt, nickel)
● Non-magnetic materials are materials that are not attracted to magnets
and cannot be magnetized (e.g. glass, plastic)
Induced magnetism:
● Magnetic materials can be magnetized by induced magnetism:
○ They can be magnetized by stroking them with a magnet, hammering
them in a magnetic field, or putting them inside a coil with a direct current
through it.
○ They can be demagnetised by hammering them, heating them or putting
them inside a coil with an alternating current through it.
● Magnetic materials that can be permanently magnetized are described as
magnetically hard (e.g. steel). Magnetic materials that are only temporarily
magnetized are described as magnetically soft (e.g. soft iron).
Permanent magnets vs electromagnets:
● Permanent magnets are a hard-magnetic material that has been
permanently magnetized
whereas electromagnets consist of a coil of wire wrapped around a
magnetically soft core and can be turned on and off.
● Permanent magnets are more useful when they do not need to be turned
off such as a
fridge magnet, whereas electromagnets have the ability to be turned on
and off so they can be used for situations such as moving scrap metal.