Transcript Electromagnetism Unit 2014

Catalyst
1. How are frequency and wavelength
related? They are INVERSELY related. As
one goes UP, the other goes DOWN!
2. What are the 3 primary colors of
light? When combined, what do they
create? RED, BLUE, GREEN. Create
WHITE light!
3. Draw a convex and concave
lens.
Magnets!
A little intro…
• http://video.nationalgeographic.com/video/k
ids/cartoons-tv-movies-kids/i-didnt-knowthat-kids/idkt-magnets-kids/
Properties of Magnets
•A magnet is any material that
exerts a magnetic force.
•Magnets attract or repel other
magnets.
•One part of a magnet will always
point north when allowed to swing
freely
Magnetic Fields
•The magnetic field is the area of
magnetic force around a magnet
•Allows magnets to interact without
touching
•Magnetic field lines are the invisible
lines that map out the magnetic field of
a magnet
•Form complete loops, never cross
•Always leave north and enter south
•Distance between field lines indicate the
strength of the magnet
•Closer the lines, stronger the lines
Magnetic Domains
•A magnetic domain is a region
where the magnetic fields of all
atoms are lined up in one direction
•If the material is NOT
magnetized, the magnetic domain
points in random directions
•If the material is considered a
magnet, the magnetic domains
are arranged in the same direction
Magnetic Materials
•A ferromagnetic material is a material that
shows strong magnetic properties
•Behaves like a piece of iron
•Iron, nickel, cobalt, samarium
•Alloy magnets - magnets made from several
different metals
•Alnico - aluminum, nickel, iron, cobalt
•Platinum and cobalt
•Ferrite - mixture of substances that contain
ferromagnetic elements
•Most commonly used today
•Brittle material but inexpensive
Mythbusters: Magnets
Can magnets be used
to climb a wall?
Making Magnets
•Unmagnetized material can be magnetized by:
•Placing an unmagnetized ferromagnetic
material in a strong magnetic field
•Rubbing the material with one pole of a
magnet
•Magnetizing a paper clip
•Rub the paperclip in one direction along one
pole of the magnet
•Magnetic field of the magnet causes some
domains in the paperclip to line up.
Destroying Magnets
•Temporary magnet is a magnet made from a
material that easily loses its magnetism
•Permanent magnet is a magnet made from a
material that keeps its magnetism for a long
time
•No magnet can last forever
•Ways to demagnetize magnets
•Drop it
•Strike it
•Heat it
Breaking Magnets
•Break a magnet in half and you will have two
smaller magnets
•Each smaller magnet has its own north pole
and south pole
•Magnetic poles are lined up in one direction,
which will remain even if the magnet is broken
S
N
Electricity
Static Electricity
• The buildup of charges on an object is called static
electricity
• Static discharge is the movement of charges from one
object to another.
– Think of this like shocking yourself when you drag
your feet on the carpet and touch a door handle.
– You feel the “shock.”
– What you really experienced is static discharge.
– Lightning is also a discharge of static electricity!
A Message from…Bill Nye
• http://www.youtube.com/watch?v=Z77IzaXGcg
How are charges transferred?
3 ways:
• Friction – rub 2 objects together
• Conduction – direct contact (touching)
• Induction – without touching
– Van der Graaff is a GREAT example!
Electric Currents
A message from our sponsor
• http://www.youtube.com/watch?v=gixkpsrx
k4Y
Electric Current
• Electric current is the continuous flow of electric charges
(electrons) through a material.
• Measured in amps (A)
• Amps = amount of charge flowing past a given point
each second.
• AC = Alternating Current (runs in BOTH directions)
• DC = Direct Current
(runs in ONE direction)
Conductors and Insulators
• A conductor is a
material through
which charges can
flow easily.
• An insulator is a
material through
which charges cannot
flow easily.
Circuits
• In order for electric
current to exist, a
circuit must first
exist.
• An electric circuit is
a complete,
unbroken path
through which
electric charges can
flow.
Voltage
• Potential energy is capacity to do work.
• Batteries provide electrical potential energy
• Voltage is the difference in electrical potential
energy between two places.
– This can also be called potential difference
– Voltage causes current in an electric circuit
– Basically, it is the amount of force pushing an
electric current
– Measured in Volts (V)
Resistance
• Resistance is the measure of how difficult it is for
charges to flow through a material.
• Increase the resistance, decrease the current
• Measured in ohms
• Best Wire = SHORT, FAT, COLD!
• Insulators = HIGH resistance
• Conductors = LOW resistance
Electromagnetism
The Maglev Train
Can a magnet be used to make a
train reach speeds of 2,000 mph?
Electric Current & Magnetism
• Wherever there is electricity, there is
magnetism
• An electric current produces a magnetic field
• This relationship is called electromagnetism
Parts of an Electromagnet
Wire to wrap
around the
core,
preferably
made of
copper. We
call this wire a
SOLENOID!
Ferromagnetic
material for a
core, like a nail
Energy Source
like a battery
Common Examples: credit cards, doorbells, radios, cranes,
refrigerators, computer hard drives, VHS tapes, microwaves,
etc.
Benefits of Electromagnets
– It can be turned on and off
– It can have its direction reversed
– We have control over the strength
How can we manipulate
Electromagnets?
• Change the number of coils of the solenoid.
– More coils = stronger
– Less coils = weaker
• Change the ferromagnetic core
– More iron = stronger
– Less iron = weaker
• Change the source
– Higher voltage = stronger
– Lower voltage = weaker
Apply it??
• Kinda Creepy??
http://videos.howstuffworks.com/discovery/40183-mythbusterselectromagnetic-turkey-video.htm
• James Bond?
http://videos.howstuffworks.com/discovery/32911-mythbustersclips-electromagnetic-watch-video.htm
• Boom?? http://science.howstuffworks.com/7102electromagnetic-pulse-bomb-video.htm
Series and
Parallel Circuits
Introduction and Overview
• http://www.youtube.com/watch?v=x2EuYqj
_0Uk
Series Circuit
• Only ONE path.
• Resistance is constant.
• If one bulb goes out, the
entire strand goes out.
• The more lights you add,
the dimmer the strand
becomes.
• The resistance is shared
equally.
Series Circuit
• Benefit: safety switch
• Drawback: a DC flow
(direct current in ONE
direction)
• Examples: security
systems, OLD Christmas
lights
Parallel Circuit
• Multiple paths for
current to flow.
• Resistance varies.
• Light may shine
brighter based on
resistance.
• Bulbs will stay lit even
when a light burns out
or breaks.
Parallel Circuit
• Benefits: very
controllable; more
dependable
• Drawbacks: voltage and
resistance vary, harder to
turn off due to being an
AC flow (alternating
current)
• Examples: wiring in
your home, NEW
Christmas lights
Side by Side
Series
Parallel
Series and Parallel Circuits Game
• http://scienceofeverydaylife.discoveryeduca
tion.com/views/other.cfm?guidAssetId=D1
507F6E-09C3-4E7B-B1E9-16708E402009