Study Notes
Magnetism and electromagnetism involve the study of magnetic forces and fields, as well as the use of electromagnets. Magnets have specific properties, and their fields can be visualized with field lines. Electromagnets are magnets created by electric currents and can be controlled by turning the current on or off.
- Magnetism — the force exerted by magnets that can attract or repel certain materials.
Example: Lodestone attracting iron pieces. - Bar Magnet — a permanent magnet with two poles, north and south, that cannot be turned off.
Example: A fridge magnet. - Magnetic Field — the area around a magnet where magnetic forces are exerted.
Example: The space around a bar magnet where it can attract iron filings. - Electromagnet — a type of magnet whose magnetic field is produced by an electric current.
Example: A coil of wire with a current running through it, used in scrapyards to lift cars. - Induced Magnetism — temporary magnetism in a material when it is placed within a magnetic field.
Example: Iron nails becoming magnetic when near a magnet. - Magnetically Hard — materials that can be permanently magnetized.
Example: Alloys of iron, nickel, and cobalt. - Magnetically Soft — materials that can only be temporarily magnetized.
Example: Iron alloys with less iron content.
Exam Tips
Key Definitions to Remember
- Magnetism: The force exerted by magnets.
- Bar Magnet: A permanent magnet with north and south poles.
- Magnetic Field: The area around a magnet where forces are exerted.
- Electromagnet: A magnet created by an electric current.
Common Confusions
- Confusing permanent magnets with electromagnets.
- Misunderstanding the direction of magnetic field lines.
Typical Exam Questions
- What word best describes bar magnets?
Permanent - What do opposite poles do?
Attract - Specifically in which direction do the lines run in a field diagram?
North to south - Why is iron usually used for the core of an electromagnet?
Because it enhances the magnetic field. - What would happen if you used steel instead?
It would retain some magnetism after the current is turned off.
What Examiners Usually Test
- Understanding of the properties of magnets and magnetic fields.
- Ability to differentiate between permanent magnets and electromagnets.
- Knowledge of how electromagnets work and their applications.