Producing Electric Current - District 273 Technology Services
Transcript Producing Electric Current - District 273 Technology Services
Section 8.3: Physical Science
From Mechanical to Electrical
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
How can a magnet produce a current in a wire?
ME due to the motion of the wire or magnet is
converted to electrical energy
Electromagnetic induction &
Producing an electric current by moving a loop of wire
through a magnetic field or moving a magnet through a
Machines that produce electric current by rotating a coil
of wire in a magnetic field
Wire coil is wrapped around an iron core and placed
between the poles of a permanent magnet.
Coil is rotated by an outside source of mechanical energy
Examples: 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 current reverses direction
The current changes direction twice with each revolution
A generator that is used in a car is known as an alternator
Electricity in the home comes from a power plant
with huge generators
When 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 plant
Electromagnets contain coils of wire wrapped around
Rotating magnets connect to a turbine
Turbine: large wheel that rotates due to
Hoover Dam and Hydroelectric Power
Sources of electricity: http://www.teachersdomain.org/resources/phy03/sci/phys/energy/energysource/index.html
Direct and Alternating Currents
Compare and contrast current in batteries and
Compare: Both devices move electrons through the wire
Contrast: 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
A 60-Hz alternating current changes direction 120
times per second
To make electric energy safe for your home you must:
Use a transformer- increases or decreases voltage
Transformers are made up of 2 coils (primary and
scondary_ wrapped around an iron core.
Alternating current in a primary coil creates a
changing magnetic field around the iron core, which
induces an alternating current in the secondary coil
Step – up transformer increases voltage. The
secondary coil has more turns than the primary coil
Step-down transformer decreases voltage. The
secondary coil has fewer turns than the primary
Power carried in power lines as high as 750,000
volts is reduced by step-down transformers to
household current (AC) of 120V
What happens to electrical energy as it passes
through a wire?
Some is lost as heat due to resistance of the wire
Why is electrical energy transmitted at high
To prevent loss of energy as heat