Recap: Chapter 22 – Magnetism - TeacherWeb

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Oct 18, 2013 (3 years and 9 months ago)

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Recap: Chapter 22


Magnetism


1.

What is a ferromagnetic material? List three common ferromagnetic elements.


A material with strong magnetic properties


like iron, nickel, and cobalt.


2.

A north pole of a magnet will _
REPEL
_ the north pole of a seco
nd magnet. A south pole of a magnet will _
REPEL
_ a
south pole of a second magnet. A north pole of a magnet will _
ATTRACT
_ a south pole of a second magnet. A north pole
of a magnet will _
ATTRACT
_ a ferromagnetic material. A south pole of a magnet will _
ATTRACT
_ a ferromagnetic
material.


3.

Explain how the force between two magnetic poles depends on the distance between them. How is this similar to electric
charges? How does this differ from electric charges?


THE STRENGTH OF THE FORCE BETWEEN TWO MAG
NETIC POLES IS INVERSELY PROPORTIONAL TO
THE DISTANCE BETWEEN THEM. IT IS SIMILAR TO THE STRENGTH OF THE FORCE BETWEEN
ELECTRIC CHARGE AS BOTH HAVE A DECREASE IN STRENGTH WITH A INCREASE IN DISTANCE


BUT ELECTRIC CHARGES FOLLOW AN INVERSE SQUARE LAW AND
THE MAGNETIC FIELD STRENGTH
DIMINISHES MUCH MORE RAPIDLY.


4.

What does the spacing between magnetic field lines tell you?


THE CLOSER THE LINES OF A MAGNETIC FIELD ARE DRAWN, THE STRONGER THE MAGNETIC
FIELD.


5.

Magnetic fields have direction. How is thi
s direction determined?


MAGNETIC FIELD LINES ALWAYS POINT TOWARD A NORTH POLE AND AWAY FROM A SOUTH POLE.


6.

How are magnetic poles and electric charges similar? How are they different? Which is stronger? Which is easier to
control? Which is easier t
o create?


SIMILAR: BOTH DECREASE IN FIELD STRENGTH WITH AN INCREASE IN DISTANCE, FIELDS BOTH
ATTRACT AND REPEL


DIFFERENT: CAN ISOLATE A SINGLE ELECTRIC CHARGE BUT CANNOT ISOLATE A SINGLE
MAGNETIC FIELD


STRONGER: ELECTRIC


EASIER TO CONTROL: MAGNETIC


EA
SIER TO CREATE: MAGNETIC



7.

What is the source of magnetism in materials?


MAGNETISM COMES FROM ELECTRONS IN ATOMS.


8.

Compare diamagnetic, paramagnetic, and ferromagnetic materials. Which is the most magnetic? What is the source of
their magnetism?
Etc. . .


DIAMAGNETIC: WEAKEST, INDIVIDUAL ELECTRONS ARE ALIGNED SO THEIR FIELDS CANCEL
EACH OTHER OUT AND THEY CREATE NOT NET MAGNETIC FIELD, PLACED IN A MAGNETIC FIELD
THEY BECOME
VERY VERY WEAKLY

MAGNETIC



PARAMAGNETIC: FIELDS FROM INDIVIDUAL ELECTR
ONS DO NOT CANCEL OUT AND THEY ARE
WEAKLY MAGNETIC AND THE ATOMS ACT LIKE MINI MAGNETS, BUT THE ATOMS ARE NOT
ARRANGED IN ANY SPECIFIC ORDER SO MOSTLY THE FIELDS OF THE ATOMS CANCEL ONE
ANOTHER OUT, IN THE PRESENCE OF A MAGNETIC FIELD THE MATERIAL WILL BEC
OME WEAKLY
MAGNETIC



FERROMAGNETIC: THE FIELDS FROM THE ELECTRONS DO NOT CANCEL EACH OTHER OUT AND THE
ATOMS ARE ACTUALLY ARRANGED IN DOMAIS THAT HAVE SIMILAR MAGNETIC FIELDS CREATING
MAGNETIC DOMAINS AND A STRONGLY MAGNETIC MATERIAL


9.

If all materials
contain moving electrons, why is the magnetism in most materials too weak to measure?

IN GENERAL, MOST OF THE FIELDS OF THE INDIVIDUAL ELECTRONS CANCEL EACH OTHER OUT
BECAUSE OF THEIR RANDOM ARRANGEMENTS.



10.

What are magnetic domains? In what type of m
aterial do they occur?

MAGNETIC DOMAINS ARE REGIONS WHERE THE ATOMS ALL HAVE SIMILAR MAGNETIC
ORIENTATION. THEY OCCUR IN FERROMAGNETIC MATERIALS.


11.

Compare hard and soft magnets.

HARD MAGNETS


HARD TO MAKE BUT ALSO HARD TO DE
-
MAGNETIZE

SOFT MAGETS


EASIER TO MAKE BUT EASIER TO DE
-
MAGNETIZE


12.

How can you create a permanent magnet? List two different ways? Why do these procedures create a permanent magnet?


(1) PLACE A FERROMAGNTIC MATERIAL IN A STRONG MAGNETIC FIELD.


(2) RUB A STRONG MAGNET IN
A SINGLE DIRCETION ACROSS A FERROMEGNETIC MATERIAL.

THIS WORKS BECAUSE IT CAUSES THE DOMAINS OF THE FERROMAGNETIC MATERIAL TO BE
ALIGNED


13.

Name three ways a magnet may be de
-
magnetized? Why do these processes de
-
magnetize a magnet?


(1) DROP IT, VIBRAT
E IT, OR STRIKE IT REPEATEDLY


(2) HEAT IT TO A HIGH TEMPERATURE


(3) FORCE SIMILAR MAGNETIC FIELDS TOGETHER


THIS DE0MAGNETIZES MAGNETS BECAUSE IT CAUSES THE DOMAINS TO BECOME MISALIGNED


14.

Where is the magnetic north pole located with respect to the Ea
rth’s geographic poles?


THE EARTH’S MAGNETIC NORTH POLE IS LOCATED AT THE GEOGRAPHIC SOUTH POLE.


15.

How is a compass used to determine direction?

A COMPASS USES THE EARTH’S MAGNETIC FIELD. ITS NEEDLE IS A SMALL MAGNET THAT
ALIGNS WITH THE MAGNETIC FIEL
D OF THE EARTH. THE NORTH POLE OF THE MAGNET LINES
UP WITH THE SOUTH POLE OF THE EARTH.


16.

What do scientists believe to be the source of the earth’s magnetic field? By what process is this field created?


THE SOURCE OF THE EARTH’S MAGNETIC FIELD IS TH
E MOLTEN METALLIC CORE OF THE EARTH.

THE HOT, DENSE MOLTEN CORE MADE OF IRON, NICKEL, AD OTHER METALS CIRCULATES INSIDE
THE EARTH CREATING ELECTRIC CURRENTS WHICH IN TURN CREATES A MAGNETIC FIELD IN
ADDITION TO ITS ELECTRIC FIELD.


17.

What evidence do sci
entists have to support the theory that the poles of the Earth are constantly changing?


THEY HAVE STUDIED THE MAGNETIC FORMATIONS IN OCEANIC ROCKS.


18.

What is magnetic declination?

MAGNETIC DECLINATION IS THE DIFFERENCE BETWEEN THE COMPASS DIRCETION AND

TRUE
GEOGRPAHIC NORTH.


19.

The magnet shown in the diagram is dropped and breaks into
three pieces. Recopy the diagram of the pieces and label the
north and south poles.


20.

A compass is located at point X near a bar magnet
as shown in the diagram t
o the left. Which diagram
shows the proper direction of the compass needle?

NEEDLE B


21.

Which diagram to the right best represents the
magnetic field near a bar magnet?

DIAGRAM 2