Magnetism and Electromagnetism
Magnetic fields surround all magnets, running from north to south poles. You can visualise these invisible force fields using iron filings - they'll line up along the field lines! The closer the field lines, the stronger the magnetic force.
Permanent magnets always have their own magnetic field, whilst induced magnets only become magnetic when placed in another magnetic field. This is why a magnet can pick up paperclips, which then attract more paperclips in a chain.
Solenoids are coils of wire that create powerful, uniform magnetic fields when current flows through them. Inside a solenoid, the magnetic field is strong and uniform, whilst outside it behaves like a bar magnet with distinct north and south poles.
Electromagnetic induction is the principle behind generators, transformers, and motors - basically most of our electrical technology. When you move a magnet near a coil of wire, you induce a current. This fundamental principle powers everything from bicycle dynamos to massive power stations.
Key Point: Solenoids are incredibly useful because you can control their magnetic strength by changing the current - perfect for electromagnets and motors!