First Principles - Sustainable Design: The Science of Sustainability and Green Engineering - page 48

the law is that the sum of all forms of energy remains constant:
E

= constant (2.3)

At this point, we should define what we mean by work. Work ( W ) is the act
of changing the energy of a system or a body. An external force does external
work; internal work is done by an internal force. Work is positive when the force
is acting in the direction of a motion, helping to move a body from one location
to another, and work is negative when the force acts in the opposite direction
(e.g., friction can only do negative work in a system).

Sidebar: Applying the Synthovation/Regenerative Model:
Electromagnetic Radiation
Heat and light are major concerns for design. The design of buildings is all
about the right amount of each. Also devices such as computers and medical
implants must dissipate heat without harming the patient. At the planetary
scale, the greenhouse effect involves conversion of light to heat. To the physi-
cist, heat and light are forms of electromagnetic radiation (EMR), which com-
prises wave functions that are propagated by simultaneous periodic variations
in electrical and magnetic field intensities (see Fig. S2.1).

Amplitude

Peak

λ

High
frequency

λ

Trough

t = 0 sec t = 1 sec

λ

Low
frequency

λ

Figure S2.1 Electromagnetic radiation. The amplitude of the
wave in the top chart is higher than that in lower chart. The bottom
wave is 2.5 cps (2.5 Hz). The top wave is 3.5 Hz, so the bottom
wave has a frequency that is 1 Hz lower than that of the top wave.