Magnets 0381999629, 9780381999629

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IRVING

AND RUTH ADLER

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http://www.archive.org/details/magnetsOOadle

The "Reason Why" Books

MAGNETS Irving

and Ruth Adler

The John Day Company

New

York

The "Reason Why" Books Irving

and Ruth Adler AIR

ATOMS AND MOLECULES COAL EVOLUTION FIBERS

HEAT HOUSES INSECTS AND PLANTS IRRIGATION: CHANGING DESERTS TO GARDENS

MACHINES MAGNETS NUMBERS OLD AND NEW NUMERALS NEW^ DRESSES FOR OLD NUMBERS OCEANS :

RIVERS

SHADOWS STORMS TASTE, TOUCH AND SMELL THE earth's crust THE STORY OF A NAIL THINGS THAT SPIN WHY? A BOOK OF REASONS WHY AND HOW? A SECOND BOOK OF REASONS YOUR EARS YOUR EYES © copyright 1966 by Irving and Ruth Adler must not be reproany form without permission. Published by The John Day Inc., 62 West 45th Street, New York, N.Y. 10036, and me day in Canada by Longmans Canada Limited, Toronto,

All rights reserved. This book, or parts thereof,

•,

J

f

Congress Catalogue Card Number: 66-15091.

ured

-7

A2^

in the

United States of America

Contents

Magnets

4

Strongly and

Weakly Magnetic Things

6

Making a Magnet

6

The

8

Poles of a

Magnet

Magnetic Fields

11

Combined Magnets Magnets Made by Electric Currents

13 16

An

18

Electric

Charge

Electric Current

in a

Magnetic Field

Made by Magnets

Waves the Atom

22

Electromagnetic

23

Magnetism

25

Two

in

Kinds of Magnetic Things _

The Magnetism

of Iron

28 30

Other Magnetic Materials

34

Very Strong Magnetic Fields

36

The Magnetism

40

Magnetism

Word Index

List

of the Earth

of the

Sun and Galaxy

44 46

47

Magnets

A

toy magnet can pick

up small

pieces

of iron.

There are many man-made magnets that are not toys.

we

Some

use every day.

ing compass

is

are parts of things that

The needle

in a scout-

a magnet. There

is

a

mag-

net in an electric bell and in a telephone receiver.

There are magnets

in

electric

motors. There are also magnets in radio sets

and

in a television picture tube.

Some magnets

are not

made by man,

but are found in nature. In

magnet ever used

is

a kind of stone.

ancient Greeks found

kind in the

fact, the first

many

district of

The

stones of this

Magnesia (mag-

^ NEE-shuh). For

now

this

reason the stone

is

(MAG-nuh-tite

—

called magnetite

stone found in Magnesia), and anything that behaves like

it is

called a magnet.

Actually there are small and large mag-

The

nets everywhere in nature.

magnets

we know

atoms of which

all

are found inside the

The

The

things are made.

planet Earth, on which large magnet.

smallest

The sun

we

live, is

a very

also a

magnet.

galaxy, a family of over one

hundred

billion stars,

magnet

is

one of which

is

the sun,

is

a

too.

This book

tells

you about

all

these

mag-

nets that are in the atoms, on the earth,

and among the

stars.

(1)

Weakly Magnetic Things There are some things that a magnet will cling to. If they are small enough, it can pick them up. Things that a Strongly and

magnet can

cling to or pick

up

are said to be strongly

magnetic.

There are other things that a magnet to nor pick up.

These things are said

will neither cling

to

be weakly mag-

netic. If

you have a toy magnet, you can see

for yourself

which things are strongly magnetic and which are weakly magnetic.

A magnet will pick up a paper clip made of iron. cling to a pot cover

made

It

will

of stainless steel. So iron

and

steel are strongly

magnetic. Other strongly magnetic

materials are nickel

and cobalt.

A magnet

will not pick

up

pick, a brass curtain ring, a glass tumbler, or

or cling to a

copper penny, a

an aluminum

pot.

and aluminum are

per, silver, glass

wooden silver

tooth-

dime, a

So wood, brass, copall

weakly magnetic.

Making a Magnet Anything that

is

a magnet. For example, an ordinary iron if

is

not a magnet.

a magnet

is

It will

not pick up another

held very near the

pick up another

made into paper clip made of

strongly magnetic can be

clip.

clip,

clip.

But

then the clip will

This shows that a piece of iron that

Direction of rubbing

To magnetize a needle rub it many times tion with one end of a magnet.

is

in

only one direc-

brought near a magnet becomes a magnet

itself.

We

say that the iron near the magnet has been magnetized,

and that

it

has gained magnetism.

If

the iron

is

then

moved far away from the magnet, it loses its magnetism. The harder the iron is, the more slowly it loses its magnetism. If a needle made of steel, which is a hard iron, is magnetized time. is

A magnet

called a

A

in this

way,

that holds

better

Be

holds its

its

magnetism

magnetism

for a long

for a long time

permanent magnet.

way

to

magnetize a needle

times with a magnet. net.

it

sure to rub

it

Rub

is

to

rub

it

many

it

with only one end of a mag-

in only

one direction, from one end

of the needle to the other end.

Another way of making a magnet 17.

is

described on page

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