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Alternating and Direct CurrentDirect Current (DC) is the one way flow of electrical
charge from a positive to a negative charge. Batteries produce direct current.Direct Current is different than alternating current
because the charge only flows in one direction.Alternating Current (AC) is when charges
flow back and forth from a source.It is the way we receive our electricity (for our
houses, businesses, etc.)The purpose of transformers is to convert AC
voltages.Transformers are extremely important to AC
current, and our life.
From Mechanical to Electrical Energy
A magnet can produce an electric current-Moving a loop of wire through a magnetic
field causes electric current to flow in the wire
Moving a magnet through a loop of wire has the same effect
How can a magnet produce a current in a wire? Due to the motion of the wire or magnet is
converted to electrical energy
Electromagnetic induction & GeneratorsElectromagnetic Induction
Producing an electric current by moving a loop of wire through a magnetic field or moving a magnet through a wire loop
http://www.youtube.com/watch?v=uoQelu7XRjk
GeneratorsMachines that produce electric current by
rotating a coil of wire in a magnetic fieldWire coil is wrapped around an iron core and
placed between the poles of a permanent magnet.
GeneratorsCoil is rotated by an outside source of mechanical
energyExamples: Steam, wind, water
As the coil turns in the magnetic field, electric current flows through the wire
When the coil turns so that the ends move past opposite ends of the magnet: The current reverses direction
The current changes direction twice with each revolution
A generator that is used in a car is known as an alternator
Electric GeneratorsElectricity in the home comes from a power
plant with huge generatorsWhen the coil is fixed and the magnet
rotates, the current is the same as if the coil rotates and the magnet is fixed.
Construction of a generator in a power plantElectromagnets contain coils of wire wrapped
around iron coresRotating magnets connect to a turbineTurbine: large wheel that rotates due to
Brain POP Sources of electricity: http://www.teachersdomain.org/resources/phy03/sci/phys/energy/energysource/
index.html
Direct and Alternating CurrentsCompare and contrast current in batteries
and generators: Compare: Both devices move electrons through
the wireContrast: Batteries have DC. Generators have AC.
DC- Direct Current- Flows in only one direction.
AC- Alternating current- reverses the direction of current flow regularly.
In N America, generators produce alternating current at a frequency of 60 cycles per second, or 60 Hz
A 60-Hz alternating current changes direction 120 times per second
http://www.pbslearningmedia.org/resource/phy03.sci.phys.energy.hooverelec/hoover-dam-and-hydroelectric-power/
https://www.youtube.com/watch?v=IwdtXGAtgvE#t=59 Harnessing Waves?