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S8P5. Students will recognize characteristics
of gravity, electricity, and magnetism as major
kinds of forces acting in nature.
b. Demonstrate the advantages and
disadvantages of series and parallel
circuits and how they transfer energy.
c. Investigate and explain that electric
currents and magnets can exert force on
each other.
Direct Current- charges always flow
in the same direction
Alternating Current- charges
continually shift from flowing in one
direction to flowing in the reverse
direction
1.Circuit
2.Electrical Current
3.Voltage
4.Resistance
• Rate at which electrical
charges (electrons) pass a
given point
• measured in amperes or
amps (A)
A measure of how much work is
needed to move a charge (current)
between two points.
• Potential difference between two
points in a circuit
• measured in volts (v)
• opposition to the amount of
current in a wire OR
“electric friction”
• measured in ohms(Ω)
• Cell or Battery - device produces electric current by
converting chemical or radiant energy into
electrical energy
• Thermocouple - device produces electric current
by converting thermal energy into electrical energy
• Photocells - device produces electric current by
converting light energy into electrical energy
• AC current is produced by a generator, usually at
a power plant.
• Power plants convert moving water, fossil fuels,
nuclear power, wind, solar energy into electrical
energy
• Why are some substances
magnetic and other
substances are not?
• A magnet is an
object that is
surrounded by a
magnetic field and
that has the
property of
attracting iron.
• The spinning electrons in every atom
produce tiny magnetic fields. In most
materials the fields of atoms point in
random directions so the magnetic
fields cancel each other out.
• In some materials the magnetic
fields of electrons align with one
another. A cluster of atoms with
magnetic fields lined up in the same
way is known as a magnetic domain.
• For an object to be
magnetic, most of its
domains (tiny magnetic
fields produced by spinning
electrons) must be aligned
in the same direction.
• A pole is the area of a magnetic
where the magnetic effect is
the strongest.
• Every magnetic has two poles –
often called the north and
south pole.
• Magnets can produce:
– An attractive force (pulling) when unlike
magnetic poles attract
– A repulsive force (pushing) when like
magnetic poles repel.
Sounds a lot like the Law of Charges!
• Magnetic force is caused by a magnet
attracting (pulling) other magnets and
some other materials (e.g. iron and
steel)
• Magnetic force is also caused by a
magnet repelling (pushing) other
magnets and some other materials
(e.g. iron and steel)
• A magnetic field is area around the
magnet in which magnetic forces act;
concentrated into a pattern of lines
that extend from the magnet’s north
pole to its south pole.
• Magnetic energy results when an
object is moved a distance by a
magnetic force.
• Two Kinds of magnets:
• a) Temporary - easy to magnetize
and demagnetize easily
• b) Permanent - hard to magnetize
or demagnetize
What is the difference
between a motor and a
generator?
What is the difference
between a motor and a
generator?
• A compass points to the Earth’s
North Pole because the Earth
acts like a giant magnet. (The
core of the Earth is mostly molten
iron.)
• Earth has a north magnetic
pole and a south magnetic
pole.
• Earth’s magnetic poles are not
exactly the same locations as the
geographic poles (axis where the
Earth spins).
• A compass can be
used to find
directions
because its needle
lines up with the
Earth’s magnetic
poles.
• What would
happen to the
magnetic
properties of a
bar magnetic if
you cut it into
two pieces?
How can a magnet lose its
magnetic properties?
• Losing Magnetic Alignment by:
– a) Dropping a magnet or hitting it
too hard
–b) Putting magnet in opposite field
for too long
–c) Increasing the temperature
• An electromagnet
is a coil of currentcarrying wire that
acts as a magnet
that can be turned
on and off.
• Solenoid = a current-carrying coil of wire
with many loops.
• When a solenoid is turned on, a magnetic
field is created.
• If a piece of iron or other ferromagnetic
material is wrapped by the coils of wire in
a solenoid, a magnet is created when the
current is turned on.
The strength of an electromagnet
can be increased by:
– 1)Increasing the electric current in the
solenoid
– 2)Increasing the number of coil loops around
the ferromagnetic material
– 3)Using a stronger ferromagnetic material
(more iron content)
• Examples of Electromagnet Uses:
• a)A doorbell or an alarm
• b)Moving junk cars
• c)Recording data on your
computer
• d)Reading the magnetic strip on
the back of a credit card
a) A doorbell or an alarm
b) Moving junk cars
d) Reading the magnetic strip
on the back of a credit card
Big Idea about
Electricity and Magnetism
Electromagnetism - interaction between
electricity and magnetism
- Magnetic forces arise from the movement
of electrical charge.
- Electrical forces arise from the movement
of a magnet (induced current)
Motors
An electric motor is a device that changes
electrical energy into mechanical energy.
All electric motors have an armature—a loop
or coil of wire that can rotate. The armature
is mounted between the poles of a
permanent magnet or electromagnet.
Generators
• A generator is a device that uses
electromagnetic induction to change
mechanical energy into electrical energy.
• An electric current is made when a magnet
moves in a coil of wire or when a wire
moves between the poles of a magnet
(electromagnetic induction).