Electromagnetism

15.1 Magnetic fields

• A magnetic compass is a tiny magnetic needle pivoted at its centre. One end of the compass is always north and the other is always south due to the Earth's magnetic field. 
• Like poles repel. Unlike poles attract
• Iron, steel, cobalt and nickel objects can be magnetised and demagnetised. 
• Permanent magnets are made of steel because they don't lose their magnetism easily.
• Iron filings form a pattern of lines on a magnet, representing the magnetic field. The filings would be more concentrated at the poles over anywhere else on the magnet because that is where the field is the strongest. The direction of a line of force is always north to south. The greater the distance a magnet is from a plotting compass, the weaker the magnet.
• Unmagnetised materials are put in a magnet field to magnetise them. The magnetic field induces magnetism in the material. Induced magnetism causes a force of attraction between any unmagnetised magnetic material placed near one end of a bar magnet. The force is always an attractive force…