MAGNETISM
In this area, the topics covered are: magnetic poles, magnetic fields, magnetic materials, electromagnetism and the use of magnets.
SUB UNIT HEADING |
DETAILS |
Magnetic Fields |
1. A magnet affects the space around it with an invisible force. This region is called a "magnetic field". 2. The strength of a magnetic field gets smaller as the distance from the magnet increases. 3. The presence of a magnetic field can be detected by showing that a piece of iron is attracted to the magnet. 4. When iron filings are in a magnetic field they form lines which show in which direction the invisible force is acting. |
Magnetic Materials |
1. Every magnet has 2 strong areas called "poles". Between its poles a magnet's field is weaker. 2. A magnet's two poles are referred to as the "North pole" and the "South pole". 3. When two similar poles are close together they repel each other. (North repels North and South repels South). 4. When two dissimilar poles are close together they attract each other. (North attracts South and South attracts North). 5. When any magnetic pole is next to a piece of ordinary iron, the magnet and the iron attract each other. 6. The only sure way to know if two objects are both magnets is if it is possible to detect a force pushing them apart. 7. The Earth's core acts as a giant magnet with poles near the North and South poles of the planet. 8. If a bar magnet is free to turn, the North pole will face north if there are no other magnets nearby. This is how a compass can be used to find direction. |
Electromagnetism |
1. Non-metals are never magnetic. 2. Iron, steel, cobalt and nickel are attracted to magnets and can be made into permanent magnets. 3. Other pure metals are non-magnetic. 4. One permanent magnet can be used to turn a piece of ordinary iron or steel into another magnet. 5. Iron is a "soft" magnetic material: it is easy to magnetise but loses its magnetism easily too. 6. Steel is a "hard" magnetic material: it is difficult to make steel into a magnet but it retains its strength for longer. 7. It is possible for a magnet to lose its magnetism if it is heated red hot or if it is hit hard. 8. The strongest modern permanent magnets are alloys (mixtures) of iron with other elements such as Neodymium. |
Use of Magnets |
1. Magnets have thousands of uses in our everyday lives. Examples include toys, motors and earphones. 2. The most powerful magnets in common use are strong electromagnets used in MRI body scanners. 3. Computer hard disk drives contain billions of microscopic magnets used to store computer data, videos and music. |
Summary Notes & Questions
Remember to continual check your past paper attempts and review unknown areas with your summary notes. Websites like BBC Bitesize and Mr MacKenzie Fizzics will also help your revision. Ask your teacher if you are unsure of how to proceed with your revision plan and to clarify areas you are unsure about.