Man's physical universe




A Number of Important Types of Energy Have Been Recognized.

The following important types of energy have been recognized:

sound, kinetic, linear, heat, electrical, chemical, radiant, volume, and


A few score years ago electrical energy was not recognized as a

type of energy, although its manifestation as lightning w^as quite

familiar; so it would appear quite possible that there are other forms

of energy concerning which we know no more than our distant ancestors

knew about electrical energy.

The following sections in this Unit will be devoted to the applications

of linear energy, which is sometimes called mechanical energy, in

doing man's work. Unit VI will be devoted to the study of radiant

energy and sound; Unit VII will take up the study of electrical energy;

and Unit VIII will consider chemical energy.

Energy May Be Transformed from One Form into Another.

Everyone is familiar with the most import energy transformations.

The radiant energy of the sun is transformed by photosynthesis into

the chemical energy of cellulose; cellulose may be burned to produce

heat, which may be used to generate steam (kinetic energy), which in

turn may be used to operate steam engines (mechanical or linear


The mechanical energy of steam engines may then be used

to turn a dynamo to produce electricity (electrical energy), and this

electricity may in turn be used to produce chemical energy (storage battery),

mechanical energy (motor), light (light bulb), or heat (stove).

Most of the energy available to man can be traced back to the sun

but radioactivity, the rotation of the earth, and radiations from the

stars furnish additional relatively small amounts of energy not commonly

useful, although tidal energy may become an important factor

in life some day.

There Is No Gain or Loss of Energy in Any Transformation.

Machines give out only as much w^ork as is

put into them, minus

the work required to overcome friction and the w^ork required to

produce forms of energy which are not useful. For example, the heat

produced by an electric-light bulb is seldom useful, and the sound

produced by an internal-combustion engine is undesirable and therefore

constitutes a problem to be solved.

Good bearings and proper lubrication provide greater efficiency by

decreasing friction.

_„ .

. , . useful output (work)

Efihiciency is the ratio: ^ ^ , .


total input ot energy

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