Download Magnetic, Electric, and Gravitational Fields

What Should I Be Doing??
Open notebook to page 114 and
write/draw everything you can
think of about magnets, magnetic
field, electricity, electric field, and
electromagnets.
Magnetic, Electric, and
Gravitational Fields
Forces between objects act when they
are in direct contact and when they are
not touching. Magnetic, electric, and
gravitational fields act at a distance.
What is a field?
• A field is a region of influence surrounding an
object.
– Example: Baseball field, battlefield, football field,
etc.
• A field model can be used to explain how 2
objects are exerting (applying) forces on each
other without touching.
• When a second object is placed in this region,
the field exerts a force on the object and can
cause the object to change motion.
• 3 types of fields
– Electric, Magnetic, and Gravitational
Electric Field
• Definition: A region where charged objects
exert forces on other charged objects.
• Examples: Light bulbs, cell phones,
batteries, TV, etc.
• Properties: Charged/Uncharged Particles
– Protons – Positive charge
– Electrons – Negative charge
– Neutrons – No charge
Electric Field
• The force between
electric charges can be
attractive or repulsive.
– Opposite charges attract
each other
– Similar charges repel
each other
• Electric force increases
as electric charges
increase.
• Electric force decreases
(weakens) with
increasing distance.
Electrical Energy
• Benefits Us: The electricity that we use is
transformed from mechanical energy to
electrical energy in power plants.
• Other examples of electrical energy
transformations:
– Batteries or cells:
Convert chemical energy into electrical energy
– Solar cell:
Convert solar energy to electrical energy
– Generator:
Converts kinetic energy into electrical energy
– Motor:
Converts electrical energy into kinetic energy
Magnetic Field
• The Science Behind Magnets:
How Do They Work:
– https://www.youtube.com/watch?v=MZtTVsIOA9c (5 minutes)
Magnetic Field
• Definition: Region where a magnet, electric
current, or a moving charged particle in which
a magnetic force exerts force on another
magnet, electric current, or charged particles.
Magnetic Field Lines
• To help us see the
magnetic field lines,
we use iron fillings
to see the lines.
– Example: Magnetic
Potential Energy Lab
• Since magnetics are
attracted to iron, we
are able to see the
field lines.
Examples of Magnetic Field
•
•
•
•
•
•
•
Magnets
TV
Cell Phones
Solar Wind
Auroras
Compass
Mid-Ocean ridges
Earth’s Magnetic Field
• Earth has a magnetic
field due to the
composition of the core
(iron and nickel).
• The Earth’s Magnetic
Field is response for
deflecting solar wind,
which are charged
particles that come
from the Sun.
Auroras
• Solar wind energizes the magnetosphere,
which causes the acceleration of elections
there
– The charged particles then interact with oxygen
and nitrogen in the upper atmosphere causing
them to emit light.
– The color depends on the type of atom that is
excited and how excited it becomes,
How Does a Compass Work?
• The North end of a
compass needle (a
magnet) points to the
geographic North
pole.
• The geographic
North pole is the
magnetic South pole.
– Opposites attract!
Evidence of Earth’s
Magnetic Field
• Remember learning about this?
– Rocks on either side of the mid ocean ridge
– Iron in molten rock lines up in the direction of
Earth’s magnetic field – when it cools into rocks,
it leaves a record of Earth’s magnetic field
strength and field direction.
Properties: Magnetic Field
• Magnets have 2
distinct, opposite
ends.
– North pole and South
pole.
– Field lines start from N
to S.
• 2 types of magnets
– Permanent magnet
– Electromagnet
Magnetic Field
• Attractive/Repulsive
– Opposite poles are attracted
to each other.
– Similar poles are repel each
other.
• Increase / Decrease
– Magnetic force increases
with decreasing distance.
– Magnetic force decreases
(weakens) rapidly with
increasing distance.
• Benefits Us:
– Earth’s magnetic field
protects us from solar wind
– Directions – Compass
Electric and Magnetic Fields are
Related! (On back side of notes)
• Magnetic fields can produce electrical
currents in conductors (copper).
• Electromagnets are temporary magnets
that lose their magnetism when the
electric current is turned off.
Electromagnets
• In 1820, Danish physicist Hans Christian Oersted
discovered that when an electric current was in a
wire, the compass needle rotated.
• If the compass needle rotated, it must have been
because of a magnetic field.
• An electric current flowing through a wire forms a
magnetic field!
• He also created aluminum for the first time!
(He was also good friends with Hans Christian Andersen, who was the
original author of “The Ugly Duckling” and “The Little Mermaid.”)
Electromagnets
• An electromagnet is a
magnet that runs on
electricity.
• An electromagnet works as
the electric current passes
through the wire, small
magnetic regions align with
the wire’s magnetic field.
• The strength of the
electromagnet can be
increased or decreased by
changing the electric
current passing through the
wires.
Electromagnets
• If the wire is twisted into a loop
(coil), the magnetic field is
increased.
• The coil of wire spinning around
a magnet can form an electric
current.
• Examples: Motors, generators,
blenders, speakers, washing
machine, and electric
toothbrushes.
– https://www.youtube.com/watch
?v=rgg1WUJhUc4 (1 minute)
Simple Electric Motors
• Electric motors turn
electrical energy into
mechanical energy.
– It contains an electromagnet
that rotates between the
poles of a magnet.
– The coil of the electromagnet
is connected to a battery or
other source of electric
current.
– When an electric current
flows through the wire in the
electromagnet, a magnetic
field is produced in the coil.
Simple Electric Motors
• The coil rotates because
like poles repel and
opposite poles attract.
• The rotating coil can be
attached to a shaft and a
blade in an electric fan.
Generators
• Generators work the
opposite way. (Turn
mechanical energy is
changed to electric
energy.)
– A coil of wire is wrapped
around an iron core.
– The wire is placed inside
a magnetic field, and the
magnets are turned
using a turbine.
• Turbines are huge wheels
that rotate when pushed
by water, wind, or steam.
Generators
• Generators at Power Plants produce electric energy
for our homes.
• Watch:
https://www.youtube.com/watch?v=d_aTC0iKO68
History: New Deal and TVA
• https://www.youtube.com/watch?v=URqvgTUekQQ
(5 minutes)
• 1930s: The dams controlled floods, improved
navigation and generated electricity.
• The most dramatic change in Valley life came
from the electricity generated by TVA dams.
• Electric lights and modern appliances made life
easier and farms more productive.
• Electricity also drew industries into the region,
providing desperately needed jobs.
Wheeler Dam –
Village, Alabama
Huffman Dam –
Dayton, Ohio
Gravitational Fields
• Definition: The region of
space surrounding a
body in which another
body experiences a force
of gravitational attraction.
• Examples: Gravity acting
on Earth and pulling
objects toward the
ground
Properties of Gravitational Field
• Weight vs. Mass
– Weight is a gravitational
force that is often
confused with mass.
– Mass is the amount of
matter a body contains
– Weight is proportional
to mass, but depends on
the gravitational field at
a particular location.
– Object on Earth will
weigh more than the
same object on the
moon.
Mass vs. Weight Video
• https://www.youtube.com/watch?v=gjfLI
7aJKmQ
Gravitational Field
• Attractive/Repulsive
– Gravity is an attractive
force since it pulls
objects toward each
other.
• Force Increases &
Decreases
– The gravitational force
increases with the mass of
the objects.
– The gravitational force
decreases (weakens) with
increasing distance.
Benefits Us?
• Keeps us on the
ground instead of
floating
everywhere!
Toys in Space
• Introduction:
– https://www.youtube.com/watch?v=khLdL3X5acY&list=PLi
uUQ9asub3Ru9GIOTbZFRa4f2R_kM0tx&index=1
• YoYo:
– https://www.youtube.com/watch?v=ZzSt8t7jsdo&list=PLiuU
Q9asub3Ru9GIOTbZFRa4f2R_kM0tx&index=3
• Jump Rope:
– https://www.youtube.com/watch?v=Kmvj6f3TPo&index=4&list=PLiuUQ9asub3Ru9GIOTbZFRa4f2R_
kM0tx
• Soccer:
– https://www.youtube.com/watch?v=Ayhuejk88CE&index=1
2&list=PLiuUQ9asub3Ru9GIOTbZFRa4f2R_kM0tx
• Climbing Bear:
– https://www.youtube.com/watch?v=hZSUUHiOeIo&index=1
0&list=PLiuUQ9asub3Ru9GIOTbZFRa4f2R_kM0tx
Acting At A Distance
(Write this underneath your notes on the lined paper)
– Magnetic Field:
• When magnets are not touching you still feel
tension or attraction between them.
– Electric Field:
• When 2 electrically charged objects meet, they
oppose each other.
– Gravitational Field:
• When an object falls, gravity is pulling it down
without directly touching the object.
Name that field!