English for students of Physics_Unit 12

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Unit Twelve
MAGNETISM
READING PASSAGE
Earth’s magnetic field
Scientists still do not know exactly what causes the earth’s magnetic field. In the 16th
century, it was believed that a mountain of magnetite (a magnetic mineral) was located at
the North Pole and that this mountain caused the earth’s magnetic field. English physician
William Gilbert was the first to propose, in 1600, that the earth itself was a massive
magnet. Current theories hold that the earth’s magnetic field is created by currents within
the liquid outer core of the earth, which is composed mostly of iron. This liquid core
contains ions, or electrically charged atoms and molecules. The motion of these charged
particles within the earth is thought to create the earth’s magnetic field.
Scientists sometimes find it easier to model the earth’s magnetic field as if it were a
perfectly symmetrical magnetic field coming from one large bar magnet. The poles of this
hypothetical magnetic field, based on averaging the direction and strength of earth’s magnetic
field, are called the geomagnetic poles. The north geomagnetic pole is located near Thule,
Greenland, 1250 km (780 miles) from the geographical North Pole. The south geomagnetic
pole is located near Vostok, Antarctica, 1250 km (780 miles) from the geographic South Pole.
Paleomagnetism is the study of the earth’s magnetic field in ancient times. Scientists can
study the earth’s ancient magnetic fields by measuring the magnetic orientation of certain
rocks. When molten rock crystallizes, crystals of magnetic minerals align with the earth’s
magnetic field. The rock thus records the direction of the earth’s magnetic field at the time of
its crystallization. By measuring the magnetic orientation and determining the age of such
rocks, scientists can measure the orientation of the earth’s magnetic field at different times in
the earth’s history. Geologists can use systematic paleomagnetic measurements on rocks of
different ages to map out the apparent movement of the earth’s magnetic field as a function of
time. This map defines what is known as a pole path. Differences in the pole paths of the
continents indicate the relative drift of these continents.
Paleomagnetic measurements played a key role in the development of the theory of plate

tectonics by providing evidence that the oceans grow from their centers outward. Strips of
alternating magnetization found in the ocean floor on either side of the mid-ocean ridges were
explained by assuming that oceanic crust continually splits and moves away from the mid-
oceanic ridges. Additional crust is continually generated in the gap by the eruption of lava,
and the solidifying lava records the orientation of the earth’s magnetic field at the time of

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solidification. The continual creation of new crust produces a record of the direction of the
earth’s magnetic field over time. Repeated reversal of the earth’s magnetic field produces
strips of alternating magnetization in the ocean floor on either side of the mid-oceanic ridge.
(From

)
READING COMPREHENSION
Exercise 1:
Answer the following questions by referring to the reading text
1.

What was considered to cause the earth’s magnetic field?
…………………………………………………………………………………………
………………………………………………………………………………
2.

What is the latest assumption about the cause of the earth’s magnetic field?
…………………………………………………………………………………………
………………………………………………………………………………
3.

What does the writer mean by “this hypothetical magnetic field” in line 13?
…………………………………………………………………………………………

………………………………………………………………………………
4.

How can scientists measure the orientation of the earth’s magnetic field in the earth’s
history?
…………………………………………………………………………………………
………………………………………………………………………………
5.

Why did the paleomagnetic measurements use to be important?
…………………………………………………………………………………………
………………………………………………………………………………
Exercise 2:
Choose the best alternative
1.

Scientists now
a.

have had enough evidence about the cause of the earth’s magnetic field
b.

is still working hard in finding the cause of the earth’s magnetic field.
c.

have not understood all about the cause of the earth’s magnetic field
2.

William Gilbert
a.

was the first to find the cause of the earth’s magnetic field.
b.

was the first to make the assumption about the cause of the earth’s magnetic
field.
c.

was the first to think that the earth itself was an enormous magnet.
3.

The term geomagnetic poles refer to:
a.

the earth’s poles in its magnetic field
b.

the magnetic poles of the earth.
c.

the magnetic as well as the geographical poles of the earth.

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4.

Scientists in ancient time study the earth’s magnetic field by measuring the magnetic
orientation and determining the age of
a.

the rocks of that time

b.

some kinds of rocks of the time
c.

a special kind of rock of that time
5.

Geologists use the result of paleomanetic measurements in order to
a.

find out the pole paths of the earth’s magnetic field.
b.

to study about the world’s continents.
c.

to map out the magnetic field of the earth’s as a function of time
Exercise 3:
Match each word in column A with its definition in column B

A B
1.

mid-ocean ridge
2.

strips
3.

eruption
4.

role
5.

orientation
6.

crystallization
7.

symmetrical
8.

magnetization
9.

solidification

a.

the act of something coming out very suddenly and
violently
b.

the process of turning into crystals
c.

a particular function

d.

having two halves which are exactly the same, except
that one haft is the mirror image of the other.
e.

long narrow pieces of something
f.

the area in the middle of the ocean
g.

the direction an object faces or the direction of the line
along which the body exists
h.

the process in which a liquid or semi-liquid turns into a
solid
i.

the process of giving a substance the power to draw
iron and other metals towards it.



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GRAMMAR IN USE

The gerund
1. Gerund forms

A gerund is formed exactly like a present participle form of a verb (i.e. simply by adding
–ing to the end of the verb) as follows:


Active Passive
Simple
conducting being conducted
Perfect
having conducted having been
conducted

2. Implications of the gerund
a. A simple gerund refers to something happening at the same time as the action in the
main clause
Example
: Conducting such an experiment is very dangerous.
(In this case the action of conducting is at the same time with the being dangerous)
b. A perfect gerund refers to something happening earlier than the action in the main
clause
Example
: He made the report without having made enough observations.
(the action of not making observation happens before the action of making report)
It’s unnecessary to use a perfect if it is clear from the context that the time of the gerund
is earlier than the time of the action in the main clause:
The above example can be rewritten in this way: He made the report without making
enough observation. (Everyone knows that to make a report, before that enough
observations must be made for the sake of scientific accuracy).
c. To form a negative we simply add the negative word ‘not’ before the gerund
Example
: He’s afraid of not being able to complete his thesis.

3. Gerund clause
A gerund on its own or can be combined with other elements (with subject; object; or
adverbial) to form a clause:
Examples:
i.

conducting such an experiment
ii.

not being able to complete his thesis
iii.

having made enough observations
4. Functions of the gerund

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A gerund can be treated as a noun/noun phrase, so it has a wide range of uses as a
noun/noun phrase
a.
A gerund can be treated as a noun on its own or can be used to modify another
noun
Example:
1.

Neighboring molecules beneath them are set into faster motion, and heat flows into
the floor.
2.

This is called the microwave background, and is the remnant of radiation from the
‘big bang’, the giant explosion that is believed to have occurred at the beginning

of
time in the Universe.
3.

Perhaps nothing is so ingrained in our senses as the perpetual pulling of the earth on
our surroundings.
4.

The physical meaning of this new concept – mass- is related in the most intimate way
to the identity in comparing weights which we have just noted.
5.

It’s just that nothing would stop that fall, there would be no supporting force
opposing the gravitational pull, so he would feel weightless.
b.
As a subject of a sentence
Example:
1.

Sitting and observing a substance to decay is a hard work.
2.

Finding the cause of the earth’s field has taken much time of the scientists throughout
the story.
When functioning as the subject of a sentence, a gerund can be replaced by a to-
infinitive, but there is a difference between them. While a gerund refers to something in
general, a to-infinitive refers to something in a particular situation.
c.
As a complement after be
Example

: What he has to do now is quickly finishing his research.
d.
As a prepositional complement
d.1.

As a complement after a preposition following a noun

Example
:
1.

The question of finding the cause of the earth’s magnetic field has drawn a great
attention from physicists.
2.

We can not see electric current in a wire, so we find different ways of explaining
what is going on.
The following nouns with their prepositions can be followed by a gerund


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advantage of
aim of/in
amazement at
anger about/at
annoyance
about/at
anxiety about
apology for
awareness of

belief in
boredom with
danger of/in
difficulty (in)
effect of
excitement
about/at
expense of/in
fear of
insistence on
interest in
job of
matter of
objection to
pleasure
in/of
point of/in
possibility of
problem
in/of
worry about
prospect of
purpose of/in
question
about/of
reason for
satisfaction
with
success in
surprise at

task of
work of

d.2. As a complement after a preposition following an adjective
Example:
1.

This internal energy spreads out, making it much less effective at producing work
than, say, the organized kinetic energy of a moving object.
2.

Energy has been called the “common denominator” of the natural science because its
conservation law makes it so useful in understanding any physical process.

The following are the adjectives with their prepositions that can take a gerund
afraid of
amazed at
angry about/ at
annoyed about/at
anxious abut
ashamed of
aware of
bad at
bored with
capable of
content with
dependent on
different from/to
excited about
famous for

fed up with
fond of
good at
grateful for
guilty of
happy about/with
interested in
keen on
nervous of
pleased
about/with
ready for
responsible
for
satisfied with
sorry
about/for
successful in
surprised at
worried
about
wrong with
Other prepositions that are followed by a gerund
after
against
as a result
as well as
because of
besides
by

by means of
despite
for
in
in addition to
in favor of
in spite of
instead of
on account of
since
through
what about
with

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before how about on without
Example:
1.

Absorption spectra of gases may be obtained by passing white light through a sample
of gas before the light enters the prism.
2.

By measuring the magnetic orientation and determining the age of such rocks,
scientists can measure the orientation of the earth’s magnetic field at different times
in the earth’s history.
3.

Using springs of various thickness, one can make scales for measuring very large and
also very small weights.

e.
As a complement after adjectives expressing degrees of difficulty
Example
:
1.

It’s difficult detecting an element without using a spectroscope.
2.

It’s impossible keeping a car in steady speed.
Note:
Refer to the
Grammar in use
part in
UNIT ELEVEN
for these adjectives.
However, It’ is more common to use a to-infinitive instead of a gerund.
f.
As a direct object after some verbs
These verbs include some one - word verbs and some prepositional verbs
Example
:
1.

We can live quite happily without thinking about why this is so. Once we start
thinking about the force of gravity
, which makes things fall, we may come up with
some odd ideas.
2.

He’s thinking
of
taking a course of physics.
3.

Some energy goes into raising the temperature of the cylinder walls and the piston,
and that part spreads outward, doing no useful work
The following verbs take gerund as a direct object