Magnetism and electromagnetism

• A magnetic field is a region where a magnetic pole experiences a force acting on it
• A magnetic material is defined as something that can be magnetised temporarily or permanently.
• Permanent magnets remain magnetic (hard) whereas temporary magnets lose their magnetism (soft).
• The strength of the magnetic field around a permanent bar magnet decreases with distance from the magnet.
• A soft magnetic material can be induced by attracting it to a stronger magnet but it will lose the magnetism once removed
• Magnetic forces are due to interactions between magnetic fields
• In a magnet, like poles repel and opposite poles attract

  
• Like poles have similar magnetic fields so they repel because they try to push away from one another
• Opposite poles have different magnetic fields so they attract because they want to pull towards each other
• Magnetic materials that are attracted to magnets and can be magnetised (e.g. Iron, steel, cobalt, nickel)
• Hard magnetic material (permanent) would be steel
• Soft magnetic material (non-permanent) would be iron or nickel
• Non-magnetic materials that are not attracted to magnets and cannot be magnetised (e.g. glass, plastic)
• • INTO THE SOUTH OUT OF THE NORTH

  
• Magnetic materials can be magnetised by induced magnetism:

  • They can be magnetised by stroking them with a magnet or hammering them in a magnetic filed, or putting them inside a coil with direct current through it
• The magnets that are magnetised can be demagnetised by hammering them, heating them or putting them inside a coil with an alternating current through it
• Permanent magnets are a hard-magnetic material that has been permanently magnetised
• Electromagnets consists 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
• Electromagnets have the ability to be turned on and off so they can be used for situations such as moving scrap metal
• The direction of a magnetic field line shows the direction of the force on a north pole at that point
• Field strength decreases with distance from the magnet
• Charge is measured in coulombs (C)