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newton (the same apple pressing down on the hand lifting it) pressing against an
object moving at a constant velocity at 1 meter per second. When discussing electrical power, other base unit terms collectively (and self-referentially) describe the
various aspects of the electron flow. Voltage is the potential energy difference
between two points. Named after Alessandro Volta, the inventor of the battery in the
last decade of the eighteenth century, the volt is the unit of electromotive force. His
published experiments demonstrated how one metal willingly gives up its electrons
to another in the presence of a liquid electrolyte to produce an electric current.
Amperes, named after the father of electrodynamics, André-Marie Ampère,
quantifies electrical current of an electrical charge. One ampere equals 1 coulomb
(this is a group of approximately 6.242 × 1018 electrons) of electrical charge passing a given point each second. Conversely 1 coulomb is the amount of electrical
charge carried each second by 1 ampere of current.
Ohm is a measure of electrical resistance. Published in 1827 by George Ohm,
Ohm’s law states that the current through a conductor between two points is directly
proportional to the voltage across the two points. The resistance created is proportional to the current through the conductor in units of amperes which equals the
voltage measured across the conductor in units of volts, over the resistance of the
conductor in units of ohms. As the current or amperage increases, the resistance
decreases.
Electrical potential and flow can be conceptually related to water flowing from a
pressurized tank. The volume of water in the tank is similar to the electrical charge
measured in coulombs. A larger tank holds more than a smaller one. The pressure in
the closed tank determines the potential the water has to act on something outside
the tank. This is the water tank corollary of the difference in charge between two
points measured in volts. The higher the pressure, the more potential the water (or
the electrons) has to cause an effect.
Why is this important to design? More than the specific technical measurements
and units describing the effects of work done in a system, it is most important to
understand that all types of energy are interchangeable and equivalent with respect
to the work they produce and the heat byproduct created after that work is completed. The total amount of matter and energy is neither subtracted nor added in the
process. Even though nothing is lost nor gained quantitatively, much can change
qualitatively affecting the conditions on which living creatures rely.
Incremental environmental effects wrought by industrial activities that assemble
so many new physical and chemical compounds are, at times, pronounced, but most
accumulate silently over longer periods too subtle to readily discern. Many energetic reactions do no harm at all over time, but some, like those that release carbon
dioxide, sulfur dioxide, or nitrogen compounds into the ecosphere, are unequivocally linked to destabilizing environmental dynamics. Designers who consider these
basic principles are better positioned to provide alternative solutions to satisfy needs
without harmful effects.
2.6 Joule: The Official Energy Unit
newton (the same apple pressing down on the hand lifting it) pressing against an
object moving at a constant velocity at 1 meter per second. When discussing electrical power, other base unit terms collectively (and self-referentially) describe the
various aspects of the electron flow. Voltage is the potential energy difference
between two points. Named after Alessandro Volta, the inventor of the battery in the
last decade of the eighteenth century, the volt is the unit of electromotive force. His
published experiments demonstrated how one metal willingly gives up its electrons
to another in the presence of a liquid electrolyte to produce an electric current.
Amperes, named after the father of electrodynamics, André-Marie Ampère,
quantifies electrical current of an electrical charge. One ampere equals 1 coulomb
(this is a group of approximately 6.242 × 1018 electrons) of electrical charge passing a given point each second. Conversely 1 coulomb is the amount of electrical
charge carried each second by 1 ampere of current.
Ohm is a measure of electrical resistance. Published in 1827 by George Ohm,
Ohm’s law states that the current through a conductor between two points is directly
proportional to the voltage across the two points. The resistance created is proportional to the current through the conductor in units of amperes which equals the
voltage measured across the conductor in units of volts, over the resistance of the
conductor in units of ohms. As the current or amperage increases, the resistance
decreases.
Electrical potential and flow can be conceptually related to water flowing from a
pressurized tank. The volume of water in the tank is similar to the electrical charge
measured in coulombs. A larger tank holds more than a smaller one. The pressure in
the closed tank determines the potential the water has to act on something outside
the tank. This is the water tank corollary of the difference in charge between two
points measured in volts. The higher the pressure, the more potential the water (or
the electrons) has to cause an effect.
Why is this important to design? More than the specific technical measurements
and units describing the effects of work done in a system, it is most important to
understand that all types of energy are interchangeable and equivalent with respect
to the work they produce and the heat byproduct created after that work is completed. The total amount of matter and energy is neither subtracted nor added in the
process. Even though nothing is lost nor gained quantitatively, much can change
qualitatively affecting the conditions on which living creatures rely.
Incremental environmental effects wrought by industrial activities that assemble
so many new physical and chemical compounds are, at times, pronounced, but most
accumulate silently over longer periods too subtle to readily discern. Many energetic reactions do no harm at all over time, but some, like those that release carbon
dioxide, sulfur dioxide, or nitrogen compounds into the ecosphere, are unequivocally linked to destabilizing environmental dynamics. Designers who consider these
basic principles are better positioned to provide alternative solutions to satisfy needs
without harmful effects.
2.6 Joule: The Official Energy Unit