Download Magnetic Fields and Electric Currents

Magnetic Fields and
Electric Currents
April 28, 2015
How does this train go so fast?
The Science Behind the Maglev Train
Today, I can describe how a
magnetic field makes an electric
current.
April 28, 2015
Faraday’s Experiment
• Hans Christian Oersted discovered that an
electric current could make a magnetic field.
• Faraday set up an experiment to test whether
the magnetic field of the electromagnetic
would make an electric current in a second
wire.
Faraday’s Experiment
(p. 524)
Faraday’s New Discovery
Faraday noticed the galvanometer pointer moved when he connected it
to the battery. It moved again when it was disconnected.
• This showed that an electric current was present in the wires.
• Electric current in the second wire was made only when the
magnetic field was changing.
Electromagnetic Induction: the process by which an
electric current is made by changing a magnetic field.
4 Factors that Induce an Electric Current
(p. 525)
Inducing Electric Current
• An electric field is induced
only when a wire crosses the
magnetic field lines.
• An electric current is induced
because a magnetic force can
cause electric charges to move.
Electric Generator
• uses electromagnetic
induction to change
mechanical energy into
electrical energy.
the parts of an electric generator (p. 526)

How Electric Generators Work
Alternating Current
def: an electric current produced
by a generator that changes
direction.
Generators in power plants have
alternating current (p. 527) 
How Electrical Energy is Generated
• An electric generator converts
mechanical energy into
electrical energy through
electromagnetic induction.
 As
water flows down a chute, it turns a turbine. The
turbine spins the magnet of the generator, inducing an
electric current. (p. 527)
Transformers
increases or decreases the
voltage of alternating
current
• The side of a transformer that
has the greater number of
loops has the higher voltage.
Types of Transformers
• step-up transformer:
increases voltage & decreases
current.
• step-down transformer:
decreases voltage & increases
current.
how transformers change voltage (p. 528)

How you get energy to your home