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Making an electric current
with magnets
Or, The lights are on, even when nobody’s home!
Stuff you’ll be expected to know when we’re
done here….
Wire coils and magnets ---• Remember that a wire coil with electricity flowing through it has a
magnetic field.
• If there is a magnetic inside the coil, movement of the magnet will
produce an electric current in the wire
• The direction of the magnet’s
• movement affects
• the direction of the
• current
Relative motion • Generating a current can be done by either moving the magnet or
moving the wire. As long as there is relative motion, a current will be
generated.
• Because the current changes direction in a regular pattern as the
magnet moves, this is called alternating current, or AC
Direct current
• Batteries provide electricity that flows in only one direction – called
direct current or DC.
• A commutator on a coil-and-magnet generator can also change the
AC current to DC.
• Thomas Edison advocated for AC current, Nicolai Tesla advocated for
DC. If Tesla had won the argument, electricity today would be free for
everyone, and the DWP would just be the DW.
Generators in our power plants
• Generators convert the mechanical energy of movement into
electrical energy.
In the diagram to the
right,
The mechanical energy
is provided
by the wind
Mechanical energy sources
• Steam is the most common source of mechanical energy in the power
plants across the US today. The heat to create the steam can come
from a variety of sources:
•
•
•
•
•
Burning coal
Burning natural gas
Burning petroleum
Nuclear energy
Focused sunlight
• Some of these are cleaner and more renewable than others.
transformers
Where are the transformers?
What’s the assignment? Glad you asked….
• Read pages 734 - 740
• Complete “math Skills” worksheet. Page 53 from online resources.
• If you need help, check out the right margin on page 739 of the text.