- [Instructor] Electromagnetism
or the electromagnetic force
is one of the four
fundamental forces of nature.
It generates light and
energy and holds atoms,
matter, and the world
as we know it together.
Electromagnetism is a branch of physics
that studies the
interactions between electric
and magnetic fields.
All matter has an electric charge
which can be positive, negative, or zero.
Opposite charges attract
while like charges repel.
These electric forces bring
and hold atoms together.
And when atoms gain a
positive or negative charge
through the transfer of electrons,
a measurable electric field will form.
If those electrically charged
particles start to move,
the field will become a
flowing electric current
and form a magnetic field around it.
Under the right circumstances,
interacting electric
and magnetic fields can
continuously produce
and sustain one another.
This generates an electromagnetic field
that transmits waves of
electromagnetic energy,
or radiation, into space.
The intensity of this
radiation is determined
by its frequency.
These frequencies make up what's known
as the electromagnetic spectrum.
Near the middle of the
spectrum is visible light
such as light emitted by stars, fireflies,
and computer screens.
On either side are invisible
electromagnetic waves.
On one end are long,
low-frequency radio waves
that broadcast television
and radio signals,
microwaves that carry telephone
signals and cook food,
and infrared waves emitted by fires.
On the other are short,
high-frequency wavelengths:
ultraviolet, X, and gamma radiation.
Unlike low-frequency waves, these waves
can pass through the human
body making them useful
for medical applications.
While electromagnetism
has daily applications,
it's also the engine that
drives the planet as a whole.
Thousands of miles below
the Earth's surface,
a layer of liquid metals churn and flow.
This generates electric
currents that then produce
magnetic fields that
all together encompass
the entire planet.
Called a geodynamo, this
process causes Earth's poles
to attain positive and negative charges
turning the planet into
a giant electromagnet.
This phenomenon also
creates a protective layer
around the planet that shields us
from the most harmful radiation in space
leaving us to enjoy a world held together
by the strange and fundamental
force of electromagnetism.
