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Object that attracts certain other materials
Examples:Seal of refrigerator and magnets that hold notes to its door |
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Force created by a magnet
Can Act at a distance
Example: When you close a refrigerator, feel the pull before the magnet touches the metal frame |
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Strongest parts of magnet in terms of magnetism
Every Magnet has 2
Has both a north and south pole
Example: Earth's north and south pole |
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Area around magnet in which it exerts force
Cannot exert force on object too far away
Example:Piece of iron within magnetic field will be pulled toward magnet |
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| ex. Wood, magnetic fields of atoms are weak and point in different directions , magnetic fields cancel eachother out |
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Magnetic fields of a group of atoms align
Are pulled by magnets and can be made into one
Ex. Iron |
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Group of atoms whose magnetic field is aligned
Domains of magnetic material not aligned so fields cancel out |
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Ex. Paper Clip
Bring Magnet near paper clip containing iron, paper clip pulled towards magnet
As magnet nears the paper clip, domains within paper clip are attracted to the magnets nearest pole
Domains within paper clip become aligned
Paper clip develops own magnetic field
Domains return to random arrangement when stronger magnetic field removed |
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Made by placing materials in very strong magnetic field
Can be made by repeatedly stroking a piece of magnetic material in same direction with strong magnet
Aligns domains
Drop magnet or expose to high temperatures, domains shaken out of alignment weakening magnetism |
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Discovered when a piece of a lodestone was allowed to turn freely
One end always pointed north
Compass works due to Earth being a large magnet
Compass- simply magnet suspended so can turn freely
Magnetic field of compass aligned it's self with Earth's |
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Acts like bar magnet which runs through Earth's axis
Axis- Imaginary line through center of Earth which rotates
Source of magnetic field surrounds earth is motion of core
Composed mostly of iron and nickel
Charged particles flow within core
Process not yet completely understood |
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Constant stream of particles released by reactions inside Sun
Particles could be damaging to living cells if they reached the surface of Earth
Turns aside, deflects flow of charged particles
Most particles deflected towards magnetic poles
As particles approach Earth, react with oxygen and nitrogen in Earth''atmosphere
Ex. Displays known as Northern Lights |
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| An Electric Current produces a magnetic field |
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Discovered in 1800's by Hans Christian Oersted
Used battery and wire to demonstrate properties of electricity
Noticed as electric charge passed through wire needle of nearby compass moved
When turned current off, needle returned to original direction
Confirmed relationship between magnetism and electricity |
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Magnetism results from an electric current
When charged particle moves, produces magnetic field
Ex. Wire in loop- magnetism concentrated inside loop, field much stronger in middle of loop than around straight wire |
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Magnet made by placing a piece of iron or steel inside coil of wire
Metal acts as magnet and increases field of coil
Current turned off magnetic field disappears
Ex. Motor |
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Have more uses than permanent magnets because they can turn on and off
Ex. Electromagnet on crane
When electric charge flows through crane, picks up cans, when turned off, magnetic field disappears and cans drop |
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Convert energy of electric current into motion by interaction between current and magnetism
Ex. Power tools |
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1.) Like poles of magnets push each other
2.) As turns, opposite poles attract
3.) Electromagnetic poles switch, poles repel |
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In many machines and devices
Ex. CD Player
1.) Turns CD
2.) Moves laser across CD
3.) Gears change in rotation of motor to straight motion |
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Converts kinetic energy into electrical energy
Similar to motor in reverse
Ex. Cell Phone Generator |
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| How a Cell Phone Generator Works |
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1.) Turning handle provides kinetic energy to generator, causing gears to rotate
2.) Turning motion rotates coils of wire inside magnet. Produces electric current
3.) Electric current recharges phone battery |
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(DC) Electric charge flows in one direction
Produced by batteries and DC converters ex. Cell phone generator |
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(AC) flow of electric charge that reverses direction at regular intervals
Ex. Current that enters your home |
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Increases or decreases voltage
Use magnetism to control voltage
Consists of two coils of wire wrapped around in an iron ring
Ex. Step down transformers on utility poles |
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Rate at which electrical energy generated from another energy source
Ex. Power Plant-uses generators to convert kinetic energy into electrical energy |
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1.) Falling water provides energy to turn generator's turbines
2.) Shaft turns powerful electromagnet within a coil of wire generating electrical current
3.) Current sent along power lines at high voltage, Voltage level adjusted by transformers |
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Unit of measurement for power
Measure rate at which energy used by an electrical appliance
Power in Watts= Voltage x Current
Ex. On label of light bulb gives its power rating in watts |
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Unit of power equal to one thousand watts
Ex. Used in combined power rating for all appliances in room |
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| Energy Used= Power x Time |
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(kWh) equal to one kilowatt of power for a one- hour period
Ex.Building have Meters to determine how many kilowatt hours of energy used |
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