Download Quiz 10 Review – Chapter 24 - Answers

Review for Magnetism Quiz: Answers
1.
Where is the magnetic field strongest…
a. …outside a bar magnet?
Outside the magnet, the magnetic field is strongest at the poles.
b. …inside a bar magnet?
Inside the magnet, the magnetic field is strongest at the center.
2. Fill in the blanks to complete the five rules for magnetic field lines .
•
Magnetic field lines form closed loops.
•
Magnetic field lines never cross.
•
Inside a magnet, the magnetic field points from the south to north pole.
•
Outside a magnet, the magnetic field points from the north to south pole.
•
The closer together the magnetic field lines are, the stronger
the magnetic field is.
3. Direction of magnetic field:
a. Just outside the north pole of a bar magnet, does the magnetic field
point toward the magnet or away from it?
Just outside the north pole, the magnetic field points away from the
magnet.
b. Just outside the south pole of a bar magnet, does the magnetic field
point toward the magnet or away from it?
Just outside the south pole, the magnetic field points toward the
magnet.
4. What are the similarities between magnetic poles and charges?
Magnetic poles come in two types (north and south), just like charges (positive
and negative). Opposite types attract, and like types repel.
What is the principal difference between magnetic poles and charges?
There is no such thing as a magnetic “monopole.” In other words, magnetic
poles do not exist in isolation, as electric charges are able to do.
5. How do you create an electromagnet?
To create an electromagnet, wrap a core (which could be ferromagnetic,
plastic, or even hollow) with wire and connect it to a voltage source, such as a
battery. While current flows through the wire, the wrapped core will act as an
electromagnet.
6. What is the relationship between the strength of the electromagnet and the
number of turns of wire?
The more turns that an electromagnet has, the stronger it will be. The strength
of an electromagnet is directly proportional to the number of turns it possesses.
7. Name three facts about the magnetic field of the Earth.
(1) The magnetic field of the Earth is tilted away from the Earth’s rotational
axis by about 10° or 11°. This means that magnetic north/south and true
north/south are at different locations.
(2) The south pole of Earth’s magnetic field lies near true north, and the north
pole of Earth’s magnetic field lies near true south. This is necessary for
compasses to be able to point in the proper direction.
(3) Compasses will always align themselves parallel to Earth’s magnetic field,
provided no other magnetic disturbances affect them.
8. What is the Basic Law of Magnetism?
“Opposite poles attract, and like poles repel.”
9. How is a permanent magnet different from a temporary magnet?
A permanent magnet cannot be easily demagnetized, whereas the two
kinds of temporary magnets (electromagnets and induced magnets) can be
switched on and off.
10. Name four ways to weaken the strength of a magnet.
(1) Drop or strike the magnet. Strong impacts interfere with the alignment of
the magnetic domains.
(2) Break the magnet into smaller pieces. Each piece will be weaker than the
original.
(3) Heat the magnet. Heating the magnet causes the alignment of the
domains to become increasingly random.
(4) Place the magnet in an external magnetic field that is oriented to disrupt
the magnetic field of the original magnet. This can be done by placing like
poles of two magnets side by side.
11. What materials are naturally magnetic, or “ferromagnetic”?
Iron, cobalt, and nickel are all naturally magnetic, or “ferromagnetic.”
12. What type of magnet can be adjusted in strength, and how is this achieved?
Only electromagnets can be adjusted in strength. This is most easily accomplished
by varying the amount of current flowing through the wire that wraps the core,
but it can also be done by increasing or decreasing the number of turns.
13. Define each of the following characteristics of a magnet:
magnetic field:
the magnetic field measures the strength of magnetic
interaction (or force) in regions surrounding the magnet.
magnetic domain: microscopic regions inside a permanent magnet that are
magnetic themselves due to the alignment of spin in individual atoms.
poles:
areas of strong concentration of magnetic field in magnets.
14. List at least three common uses of magnets in everyday life.
Many possibilities: credit card strips, magnetic locks, bullet trains, anti-theft
systems, junkyard electromagnets, hard drives in computers, and many more.