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Appendix A -- Glossary
basal metabolic rate (BMR) — the minimum level of energy usage required in Calories per
square meter of body surface per hour to sustain the human body's vital functions in the waking
state
British thermal unit (Btu) — an energy unit; the amount of (heat) energy required to raise the
temperature of one pound of water one Fahrenheit degree at or near maximum density
(specifically, water at 39.1°F)
(hourly) basal energy requirement (BER) — the amount of energy in Calories per hour
required just to "stay alive"; does not include additional energy needed to support activities
performed; varies by gender and age and individual cellular behavior
calorie (cal) — an energy unit; the amount of (heat) energy required to raise the temperature of
one gram of water by one Celcius degree at or near maximum density (specifically, water at 4°C)
Calorie (Cal) — an energy unit; 1000 of calories, sometimes called a kilo-calorie (or kcal) in
physics situations; also called a "food calorie" just to confuse students
circuit — a path through which an electric current flows
current — a flow of charged particles (typically electrons) through a conductive material
efficiency — the ratio of output work or energy over input energy; typically expressed as a
percentage; can also relate output power to input power
electromagnetic radiation — photons of energy that radiate through space independent of
medium; has characteristics of both waves and particles; always travel at the speed of light, with
wavelength times frequency equal to the speed of light (in a vacuum, 2.9979 × 108 m/s)
Emissivity ( ) — the ratio of a surface's ability to emit radiant energy compared with the ability
of a perfect black body of the same area at the same temperature. Emissivity is a dimensionless
constant having values between 0 and 1. Perfect reflectors would have = 0. Perfect absorbers
would have = 1. A material with high emissivity is efficient in both absorbing radiation energy
as well as emitting it. Therefore a good absorber is also a good emitter.
energy — the capacity to move matter
First Law of Thermodynamics — energy cannot be created or destroyed (you can't win),
although it can change forms, and matter is one of those forms
foot·pound — an energy unit; equal to the amount of energy used when a force of one pound
acts over a distance of one foot
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Appendix A -- Glossary -- Page 1 of 3
horsepower — a power unit; delivery of 550 ft·lbs of energy per second
Joule — an energy unit; equal to the amount of energy used when a force of one Newton acts
over a distance of one meter; thus equal to a Newton·meter or a kilogram·(meter)² per (second)²
kilowatt·hour — an energy unit; commonly used for electrical energy; equal to the energy
delivered over one hour when the rate of energy delivery is held constant at 1000 watts
kinetic energy — energy of motion
Laws of Thermodynamics — laws that govern energy movements, actions, and relations; see
First Law of Thermodynamics and Second Law of Thermodynamics
nonrenewable resource — resources that are not replaced within a useful timeframe
photovoltaic cell — a device that converts light energy to electrical energy; also known as a
solar cell
potential energy — stored energy
power — the rate of energy delivery; energy per unit time
R-value — a measure of a material's ability to resist heat flow
radiation — energy emitted from a surface as photons with properties of both particles and
waves. The rate of radiative emission per unit time and per unit surface area , or radiative flux, is
represented as Q. Note that this "Q" is actually power per unit area, or P/A. In the MKS unit
system, radiative flux is given in watts per square meter (W/m²).
Second Law of Thermodynamics — when energy is converted from one form to another, there
is always a decrease in useful energy (you can't break even); in any closed system, randomness
always tends towards a maximum (heat flows spontaneously from hot bodies to cold bodies)
Stefan's Constant [or Stefan-Boltzmann Constant] (σ
σ) — 5.67 × 10-8 W/(m²·K4)
Stefan's Law (Stefan-Boltzmann Law) — radiative heat transfer from a body is equal to the
emissivity of that body times Stefan's constant times the fourth power of the temperature of that
body in Kelvins: Q = σT4
total (daily) Caloric intake — the sum of all energy food value (Calories) included in all liquid
and solid foods consumed over a 24-hour period
total (daily) Caloric requirement — the sum of all energy requirements for an individual over
a 24-hour period; includes waking and sleeping requirements and all activities performed during
the daily cycle
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Appendix A -- Glossary -- Page 2 of 3
per-capita energy demand — the average amount of energy consumed in a year per person in
the U.S. This is typcially expressed in units of Btu's per year per person or kilowatt·hours per
year per person.
watt — a power unit; the delivery of one Joule of energy per second; also the power supplied by
the flow of one ampere of current through a potential difference of one volt
work — energy expended in moving an object through a distance so long as the force required is
in the same direction as the movement
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Appendix A -- Glossary -- Page 3 of 3