Download Energy_Impact on Global - Saint Leo University Faculty

Energy & Its Impact on Global
Society
Jerome K. Williams, Ph.D.
Saint Leo University
Dept. Mathematics & Sciences
Chapter 11: Electromagnetism &
Generation Electricity
•
•
•
•
Magnetic Forces & Fields
Generation of Electricity
Transmission of Electricity
Electric Power Plant: A Last Look
Magnetic Forces & Fields
• A simple magnet acts as if there are two
centers of force, called poles, labeled north
(N) and south (S)
• Force between poles varies inversely with
distance; like poles repel and unlike poles
attract
Magnetic Forces & Fields
Single Bar Magnet with Field
Lines
Two Bar Magnets:
Opposite Poles Attract
Magnetic Forces & Fields
• 1820: Link discovered between electricity and
magnetism establishing field of study called
“electromagnetism”
• An electric current creates a magnetic field
• How can we use this?
Magnetic Forces & Fields
• A coil of wire with current passing through it
acts as a magnet, similar to bar magnet. Coil is
called a solenoid and is example of
electromagnet
• Used today in many applications as motors
and relays; magnetic field created or removed
by closing/opening a switch
Solenoid (Fig. 11.3)
Magnetic Forces & Fields
• A charged particle will experience a force
when moving in a magnetic field
• This is observed in nature as northern lights
(aurora borealis) seen near North Pole
Magnetic Forces & Fields
Magnetic Forces & Fields
• A current-carrying wire placed in a magnetic
field will experience a force causing it to move
• If wire connected to shaft, useful work is
extracted; this device is called electric motor
• To keep shaft turning, one uses alternating
current (AC)
Generation of Electricity
• If an electric current creates a magnetic field,
could a magnetic field create a current?
Generation of Electricity
• A moving magnet will induce a current in the
surrounding wire; the faster the magnet
moves, the greater the effect
• Faraday’s Law of Induction
• Electric Generators use this principle to work
Generation of Electricity
Transmission of Electricity
• Transmittal of Electrical Power over large
distances is impractical; energy losses lead to
very low efficiency
• Problem is avoided by changing voltage at
which electricity is transmitted
• Principle behind a transformer
Transmission of Electricity
Electric Power Plant: A Last Look
Problems
• 2, 5