Transformers turn
high voltage into low voltage or low voltage into high voltage.
They are an indepensible part of how we move electrical energy
around. They rely on the twin facts that currents cause
magnetic fields, and that changing magnetic fields cause
voltages. This way, a changing current in one circuit can create
voltages in another, moving energy from one circuit to the
other.
Here are photographs of two devices that make use of an
electromagnet.
![]() |
![]() |
electric bell | door chime |
The electromagnet for the door chime is just barely visible.
When the door chime button is pushed, the electromagnet turns on
and sucks the little iron rod inside itself. When the button is
released, the spring throws the iron rod against the chime, giving
a melodious "bong."
The section on electromagnetism