Transcript Electricity from Magnetism

Electricity from Magnetism
• When you use an electric appliance or
turn on a light in your home, you
probably don’t think about where the
energy comes from.
• How does a magnetic
field produce electric
current?
Electricity from Magnetism
• In 1831 Michael Faraday was able to
generate an electric current from a
magnetic field.
Electricity from Magnetism
• When a bar magnet is
thrust into a coil
connected to an
electric circuit, a
current is caused to
flow in the circuit to
which the coil is
attached. If the
magnet is withdrawn,
the direction of the
current is reversed.
Such currents are
called INDUCED
CURRENTS
Electricity from Magnetism
• The size of the
current depends on
how fast the magnet
moves in or out of the
coil, and the number of
loops in the coil.
• The phenomenon of
inducing a current by
changing the magnetic
field in a coil of wire is
known as
ELECTROMAGNETIC
INDUCTION.
Electricity from Magnetism
• Faraday showed that
the magnetic field
around a wire can be
changed by moving
either the magnet in
and out of a coil of
wire OR by moving a
wire between the poles
of a magnet.
Electricity from Magnetism
• A generator is a device that uses
electromagnetic induction to convert
kinetic energy into electrical energy.
Electricity from Magnetism
• The electric current
produced by the
generator changes
direction each time the
coil makes a half-turn.
Because the electric
current continually
changes direction, the
electric current is an
alternating current.
Electricity from Magnetism
• Another device that
relies on electromagnetic
induction is a
transformer.
• A transformer increases
or decreases the voltage
of an alternating current.
• A simple transformer
consists of two coils of
wire wrapped around an
iron ring.
Electricity from Magnetism
• In hydroelectric plants, water flowing
downhill turns a turbine. The turbine
turns the magnet of a generator,
inducing electric current.
Electricity from Magnetism
• In nuclear power
plants, thermal
energy created
by a nuclear
reaction boils
water to produce
steam which turns
a turbine.
Electricity from Magnetism
• The electric
current that
provides your home
with electrical
energy is usually
transformed 3
times before it
reaches your home.
Electricity from Magnetism
1. The power plant
produces electric
current with high
voltage. To decrease
the loss of power over
long distance
transmission, step-up
transformers increase
the voltage thousands
of times!
Electricity from Magnetism
2. The electricity travels over transmission
lines with very high voltage to a
distribution station with a step-down
transformer that lowers the voltage.
Electricity from Magnetism
3. The electric
current travels
over local power
lines to another
step-down
transformer which
lowers the voltage
again before the
current reaches
your house.