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Discovering Electromagnetism

Early writings show that people were aware of magnetism for several
centuries before the middle 1600s; however, people did not become
aware of the correlation between magnetism and electricity until the
1800s. In 1820, Hans Christian Oersted, a Danish physicist and philosopher
working at that time as a professor at the University of
Copenhagen, attached a wire to a battery during a lecture; coincidentally,
he just happened to do this near a compass and he noticed that the
compass needle swung around.This is how he discovered that there was
a relationship between electricity and magnetism. Oersted continued to explore this relationship, influencing the works of contemporaries
Michael Faraday and Joseph Henry.

Michael Faraday, an English scientific lecturer and scholar, was
engrossed in magnets and magnetic effects. In 1831, Michael Faraday
theorized that a changing magnetic field is necessary to induce a current
in a nearby circuit.This theory is actually the definition of induction.To
test his theory, he made a coil by wrapping a paper cylinder with wire.
He connected the coil to a device called a galvanometer, and then moved
a magnet back and forth inside the cylinder.When the magnet was
moved, the galvanometer needle moved, indicating that a current was
induced in the coil.This proved that you must have a moving magnetic
field for electromagnetic induction to occur. During this experiment,
Faraday had not only discovered induction but also had created the
world’s first electric generator. Faraday’s initial findings still serve as the
basis of modern electromagnetic technology.
Around the same time that Faraday worked with electromagnetism,
an American professor named Joseph Henry became the first person to
transmit a practical electrical signal. As a watchmaker, he constructed
batteries and experimented with magnets. Henry was the first to wind
insulated wires around an iron core to make electromagnets. Henry
worked on a theory known as self-inductance, the inertial characteristic of
an electric current. If a current is flowing, it is kept flowing by the property
of self-inductance. Henry found that the property of self-inductance
is affected by how the circuit is configured, especially by the coiling of
wire. Part of his experimentation involved simple signaling.
It turns out that Henry had also derived many of the same conclusions
that Faraday had.Though Faraday won the race to publish those
findings, Henry still is remembered for actually finding a way to communicate
with electromagnetic waves. Although Henry never developed
his work on electrical signaling on his own, he did help a man by the
name of Samuel Morse. In 1832, Morse read about Faraday’s findings
regarding inductance, which inspired him to develop his ideas about an
emerging technology called the telegraph. Henry actually helped Morse
construct a repeater that allowed telegraphy to span long distances, eventually
making his Morse Code a worldwide language in which to
communicate. Morse introduced the repeater technology with his 1838 patent for a Morse Code telegraph. Like so many great inventions, the
telegraph revolutionized the communications world by replacing nearly
every other means of communication—including services such as the
Pony Express.


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