Download Magnets 2-24-17

MAGNETS
2-24-17
Get out the directed reading from yesterday.
1. Any material that attracts iron is a(n) magnet.
2. The points on a magnet that have opposite magnetic qualities are the magnetic poles
3. The magnetic pole that points to the north is the magnet’s north pole.
4. The magnetic pole that points to the south is the magnet’s south pole.
5. The force that can either push magnets apart or pull them together is magnetic force.
6. The region around a magnet in which magnetic forces act is the magnetic field.
7. come from spinning electric charges in the magnets. magnetic forces
8. can push magnets apart or pull them together. magnetic forces
9. depend on how two magnets’ poles line up. magnetic forces
10. are regions around magnets in which magnetic forces can act. magnetic fields
11. shape that can be shown with lines that surround magnets. magnetic fields
12. are strongest at magnetic poles, where lines are closest together. magnetic fields
13. Whether a material is magnetic depends on its
a. density.
b. atoms.
c. shape.
d. mass.
14. As an electron moves, it makes, or induces a(n)
a. aurora.
b. ferromagnet.
c. electromagnet. d. magnetic field.
15. Materials in which the atoms’ magnetic fields cancel each other out are
a. aligned in domains.
c. not magnetic.
b. like iron, nickel, and cobalt.
d. magnetic.
16. Which of these is true when the poles of atoms line up?
a. The atoms cancel each other out.
c. The atoms make a weak magnetic field.
b. The atoms are arranged in a domain.
d. The atoms do not become magnetic.
17. Name one thing that causes domains of a magnet’s atoms to lose alignment.
Possible answers: dropping a magnet; hitting it too hard; putting the magnet in a strong magnetic
field opposite to its own; increasing its temperature
18. How do you magnetize something made of iron, cobalt, or nickel?
by rubbing in one (same) direction with one pole of a magnet
19. Why do you end up with two magnets when you cut one magnet in half?
A magnet’s domains are like tiny magnets, each with a north and a south pole. So, even small
pieces of magnets have poles.
C 20. magnet with strong magnetic properties
B 21. magnet made by an electric current
A 22. magnet that loses magnetization easily
D 23. hard to magnetize, but stays magnetized
24. Why can magnets point north? because Earth is one giant magnet.
25. T or F If you put a compass on a bar magnet, the needle points to the south pole of the magnet.
Explain.
True. A compass needle tip that points to the north is the north pole of its compass. So, it points
to the south pole of a magnet. Opposites attract.
26. Why does a compass needle point to Earth’s geographic north?
because Earth’s magnetic south pole is near Earth’s geographic North Pole.
27. What makes Earth’s magnetic field?
ELECTRIC CHARGES IN THE EARTH’S CORE (IRON AND NICKEL) THE OUTER CORE IS
LIQUID, AND THE CHARGES MOVE AS THE LIQUID MOVES. AS CHARGES MOVE, A
MAGNETIC FIELD IS FORMED.
Ch. 16 section 2-3 - Directed Reading
Section 2: Magnetism from Electricity
B 1. What kind of train uses an electromagnet to float above the track?
a. magnetic
b. maglev
c. electric
d. electronic
A 2. The interaction between electricity and magnetism is called
a. electromagnetism.
b. maglev
c. electric.
d. electronic.
B 3. Oersted discovered that electric current produces a(n)
a. electromagnetism
b. magnetic field. c. electronic.
d. electric field
A 4. The direction of a magnetic field produced by an electric current depends on the
direction of
a. the current.
b. magnetism.
c. wire.
d. batteries.
5. Who were the 2 scientists who first researched into the interaction between electricity and
magnetism?
1. Hans Christian Oersted André2. Marie Ampère
B 6. What are two devices that strengthen the magnetic field of a current-carrying wire?
a. magnetic field and magnetic force c. electromagnet and current
b. solenoid and electromagnet
d. solenoid and current
C 7. A coil of wire that produces a magnetic field when carrying an electric current is called
a(n)
a. electromagnet. b. maglev. c. solenoid. d. magnetic field.
B 8. What happens to the magnetic field if more loops per meter are added to a solenoid?
a. The magnetic field becomes weaker.
c. The magnetic field turns on and off.
b. The magnetic field becomes stronger.
d. There is no change in the magnetic
A 9. A solenoid wrapped around a soft iron core is called a(n)
a. electromagnet.
b. maglev. c. magnetic core.
d. magnetic field.
B 10. What happens to an electromagnet if the electric current in the solenoid wire is
increased?
a. The electromagnet becomes weaker.
c. The electromagnet turns on and off.
b. The electromagnet becomes stronger.
d. There is no change in the
electromagnet.
B 11. What is one thing that uses an electromagnet?
a. bicycle
b. doorbell c. computer d. solenoid
C 12. An electric motor changes electrical energy into what kind of energy?
a. electromagnetic
b. electronic
c. mechanical
d. magnetic
13. Explain what happens to an electromagnet when there is no current in the wire.
Matching
C 14. a device that converts electrical energy into mechanical energy
D 15. attached to the armature; reverses direction of electric current
B 16. a loop or coil of wire that can rotate
a. galvanometer
b. armature
c. electric motor
d. commutator
e. voltmeter
A 17. used to measure current
Section 3: Electricity from Magnetism
1. The process that causes an electric current in a changing a magnetic field is called
electromagnetic induction.
2. When electric current changes direction it is called a(n) ______________ current.
a. generated
b. electromagnetic c. alternating
d. rotating
3. Name two sources of energy that generators convert into electrical energy.
1. thermal energy from a nuclear reaction
2. wind energy used to turn turbines
3. from burning fuel, such as coal or gas
4. FALLING WATER IN A HYDROELECTRIC PLANT
Put the following steps for generating electrical energy in order from 1 to 4.
2
4. Steam turns a turbine.
1
5. Energy boils water into steam.
4
6. Electric current is induced and electrical energy is generated.
3
7. A turbine turns the magnet of a generator.
8. A device that increases or decreases the voltage of alternating current is called a(n)
a. voltmeter.
b. generator.
c. transformer.
d. electromagnet.
9. Explain why a transformer uses different numbers of loops in its primary and secondary
coils.
The number of loops in the primary and secondary coils of a transformer determines
whether It increases or decreases the voltage
Can I?
Distinguish the earth’s magnetic field.
Distinguish the field that surrounds a:
1. magnet
2. electromagnet
TOC # 33 Magnets notes
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Magnetic Poles are points on a magnet
that have opposite magnetic qualities.
The pole of a magnet that points to the
north is called the magnet’s north pole.
The opposite end of the magnet, called the
south pole, points to the south.
■ When you bring two magnets close
together, the magnets each exert a
magnetic force on the other. These
magnetic forces result from spinning
electric charges in the magnets. The
force can either push the magnets
apart of pull them together.
■ If you hold the north poles of two magnets
close together, the magnetic force will push
the magnets part. The same is true if you
hold the south poles close together.
■ If you hold the north pole of one magnet
close to the south pole of another magnet,
the magnetic force will pull the magnets
together.
■ A magnetic field exists in the region around
a magnet in which magnetic forces can act.
Why are some materials magnetic and some not?
■ In materials such as iron, nickel, and cobalt,
groups of atoms are in tiny areas called domains.
The north and south poles of the atoms in a
domain line up and make a strong magnetic field.
■ If the domains in an object are randomly arranged,
the magnetic fields of the individual domains
cancel each other out, and the object has no
magnetic properties.
■ If most of the domains in the object are aligned,
the magnetic fields of the individual domains
combine to make the whole object magnetic.
■ Losing Alignment - When domains move, the
magnet is demagnetized, or loses its magnetic
properties.
■ Making Magnets - You can make a magnet from
demagnetized material if you line up its domains
with another magnet.
■ When you cut a magnet in half, you end up with two
magnets.
Name four kinds of magnets
■ Some magnets, called ferromagnets, are made of
iron, nickel, cobalt, or mixtures of those metals.
■ Another kind of magnet is the electromagnet. This is
a magnet made by an electric current.
■ Temporary magnets are made from materials that
are easy to magnetize. But they tend to lose their
magnetization easily.
■ Permanent magnets are difficult to magnetize, but
tend to keep their magnetic properties longer.
Name two examples of the effect of Earth’s magnetic field.
■ The Earth behaves as if it has a bar magnet running through
its center.
■ The point of a compass needle is attracted to the south pole
of a magnet. Opposite poles of magnets attract each other.
■ A compass needle points north because the magnetic pole
of Earth that is closest to the geographic North Pole is a
magnetic south pole.
■ Scientists think that the Earth’s magnetic field is made by
the movement of electric charges in the Earth’s core.
■ Earth’s magnetic field plays a part in making auroras. An
aurora is formed when charged particles from the sun hit
oxygen and nitrogen atoms in the air.
Facts About Electricity
■ Electric currents produce a magnetic field
■ The direction of the field depends on the direction of the current
■ It is a force caused by electric charge
■ The two positive charges repel each other, as do the negatives
■ Travels at the speed of light (186,000 mph)