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Lesson 2 Summary
Use with pp. 482–489
Lesson 2: How are electricity
and magnetism related?
Vocabulary
electric current a flow of electric charge in a material
electric circuit a closed path along which current can flow
magnetic domain a large number of atoms with their magnetic fields
pointing in the same direction
electric motor a device that changes electrical energy to kinetic energy
generator a device that changes mechanical energy into electrical energy
In some materials, electrons move from
atom to atom causing an electric charge
to move along the atoms. Electrons have
negative charges. This causes them to push
away from each other. Electrons are pushed
from atom to atom to produce an electric
current.
Electric Circuit
A series circuit is an electric circuit
with only one path for a current to flow
through. Look at the circuits on page 483 in
your textbook. The current flows from the
negative side of the battery, through each
light bulb, and back to the positive side
of the battery. If you take out a bulb, this
causes the other bulb to go out too. Parallel
circuits have an advantage over series
circuits. They have more than one path for
the current to flow through. The second bulb
will still glow after the first bulb goes out.
Magnetic Fields
A magnetic field is the space around
a magnet in which it can affect other
magnets. A magnetic domain is made
up of a large number of atoms whose
magnetic fields are pointing in the same
direction. If you break a magnet, you will
have two smaller magnets whose magnetic
domains point in the same direction as the
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Chapter 17, Lesson 2 Summary
original magnet. Each magnet still has a
north and a south pole. Earth acts like a
giant magnet. It has a magnetic field. This
is what causes all compasses to point north.
Electromagnets
An electromagnet is made of wires wrapped
around a magnet. Electric current is sent
through the wires creating a magnetic field.
An iron core placed into the coil of wires
will make it stronger. The current in the wire
magnetizes the iron. Electromagnets only
attract magnetic objects when the current is
turned on. An electric motor is made of
an electromagnet, a permanent magnet, and
an object that changes the direction of the
electric current. An electric motor changes
electrical energy to kinetic energy.
Magnetism and Electricity
Magnetic fields can also be used to make
electric current in a wire. First, a magnet
must be moved through a wire coil. The
wire experiences a changing magnetic
field that produces a current in the wire.
A generator changes mechanical energy
into electrical energy. Generators are made
of a permanent magnet and a coil of wire.
A source of mechanical energy causes
the coil to spin in the field of the magnet.
The coil must spin in order to produce an
electric current.
Quick Study
© Pearson Education, Inc. 6
Electric Current
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Lesson 2 Checkpoint
Use with pp. 482–489
Lesson 2 Checkpoint
1. What advantage do parallel circuits have over series circuits?
2.
Sequence Look at the series circuit on page 483 of your
textbook. Describe the movement of current as it leaves the negative
side of the battery until it reaches the positive side.
3. Why can’t a magnet have just a north pole?
4. Explain how electricity and magnetism work together in a motor.
5.
Sequence Make a numbered list, in your own words, of steps in
which an electric motor changes electrical energy to kinetic energy.
See page 487 of your textbook for some help.
© Pearson Education, Inc. 6
6. Describe how electricity flows through a series circuit and a parallel
circuit, or draw diagrams on a separate sheet of paper.
7. Why does the coil have to spin in a generator?
Quick Study
Chapter 17, Lesson 2 Checkpoint
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