ELECTRICITY & MAGNETISM are RELATED
Things with an electric charge are affected by Electric forces.
When charges are moving (like an electrical current in a wire) the charges
are affected by Magnetic forces.
(1) a CURRENT in a wire GENERATES a MAGNETIC FIELD that can push on other magnetic things
(2) a changing MAGNETIC FIELD can GENERATE a CURRENT in a wire.
These two principles are the driving principles behind generators, electric motors, speakers,
read/write heads, electromagnets, transformers, and many other wonderous creations.
DEMO:
Generator/Motor:
Which key concept above (1) or (2) pertains to the motor and which one to the generator?
For the demo in lecture the magnets were electromagnets (using a wire coil) instead
of regular iron magnets---but that does not change the basic principle.