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JUDY ANN SANTOS’s infomercial on system loss produced more heat
than light. It was denounced by a politician as “deceitful,
misleading and untruthful advertising.” Two NGOs called
gratuitously for a boycott of her films.
Comparing a block of melting ice to the energy
lost during the transmission of an electric current is, at best, an
oversimplification; at worst, a false analogy.
But what raised my hackles was the explicit
cynicism of the infomercial. Corporations, particularly public
utilities, should inform, not pander, educate, if possible, not dumb
down the public.
At the moment, electricity and its associated
costs have provoked vigorous debate not only in Congress and the
mass media but also in universities, labor unions, trade
associations and foreign chambers of commerce. Perhaps it might be
helpful to review some of the bases in science of the concept of
system loss as defined by the Energy Regulatory Commission (ERC).
The rate of flow of an electric current or
current intensity between two points depends on the difference in
electric potential (also called electromotive force) between these
two points. A potential difference of, say, 20 volts produces a
current intensity of 1 ampere between points A and B. A potential
difference of 40 volts will result in a current intensity of 2
amperes. And so on.
This direct proportionality, however, between
potential difference and current intensity obtains only if the
current passes over a particular kind of wire and under particular
conditions. A change in the length of the wire or the use of a
different kind of wire will change the relationship of potential
difference and current intensity.
If 20 volts will produce a current intensity of
1 ampere in a wire measuring 1 meter, the same 20 volts will produce
only 0.5 ampere in a 2-meter long wire.
Furthermore, if the wire were made thicker, the
current intensity of a given potential difference would also
increase by the square of the diameter of the wire. Thus, 20 volts
will produce a 1-ampere current over a 1-millimeter thick wire but
will produce 4 amperes through an equal length of wire that’s
2-millimeters thick.
The material the wire is made of is also
important. If 20 volts will produce a current of 3 amperes in a
copper wire, it will produce only 2 amperes in a gold wire and 1
ampere in a tungsten wire all three of the same length and
thickness.
The technical term for all this is resistance. A
doubling of the length of the wire or a doubling of its thickness
doubled its resistance or reduced its resistance, respectively.
Using tungsten instead of copper increased resistance three times.
Resistance is measured in ohms. Sometimes it’s
necessary to use conductance rather than resistance. Conductance is
the reciprocal or inverse of resistance. Hence, a pathway with a
resistance of 1 ohm has a conductance of 1/1 or 1 mho (ohm spelt
backward) but now called siemens. Resistance of 30 ohms is 1/3
siemens and so forth.
The following equations can be derived.
Symbolizing potential difference by E, current intensity by I and
resistance by R, Ohm’s law can be expressed as R=E/I that, by
transposition, can also be written as I=E/R and E=IR.
Georg Simon Ohm, a German physicist, formulated
this law in 1827 using by analogy the formulae of the flow of heat
along a metal rod that the French mathematician, Jean Baptiste
Fourier, devised.
At this point it’s necessary to introduce some
terms that are germane to this exposition: ampere, coulomb, joule,
watt and volt all named after their originator.
The definitions are from The New Shorter Oxford
English Dictionary.
An ampere is a unit of electric current equal to
the flow of 1 coulomb per second.
A coulomb is the quantity of electricity
conveyed in 1 second by a current of 1 ampere.
A joule is a unit of electrical energy equal to
the amount of work done (or heat generated) by a current of 1 ampere
acting for 1 second against a resistance of 1 ohm.
A watt is a unit of electrical power (or rate of
heat generation) represented by a current of 1 ampere flowing
through a potential difference of 1 volt. It’s also equivalent to
the production of 1 joule of energy per second.
And finally, a volt is the difference of
electric potential capable of sending a constant current of 1 ampere
through a wire whose resistance is 1 ohm.
Most people, especially politicians, use energy
and power as interchangeable terms. They are not. You will also
notice in these definitions that time is critical in any discussion
of electricity. It’s obvious, but again most people forget, that
electricity cannot be stored; once produced it’s immediately
consumed. Time of use affects its market pricing which, in general,
is calculated at peak demand.
The resistivity of metals vary. The best
conductor is silver, followed by copper and close behind are gold
and aluminum.
Since electricity is produced by the movement
and transfer of electrons, energy loss is due to the resistance of
the conductor. If the temperature of the conductor rises, the atoms
in it vibrate more rapidly making it more difficult for electrons to
get through consequently producing less electricity. Scientists use
a constant—the temperature coefficient of resistance—to
calculate the fractional increase in resistance per degree Celsius.
We see from all this that by using Ohm’s law
we can figure with great exactitude the amount of energy lost. At 0
degrees Celsius, 1 ohm can be defined as 1 volt per ampere.
Since power is energy per unit of time, energy
is power multiplied by time. The unit of energy that utilities use
for billing is the kilowatt-hour. One kilowatt-hour is equal to
3,600,000 joules. A 100-watt incandescent light bulb, burning for 24
hours, uses 2.4 kilowatt-hours of energy. Lifeline subsidies can
then be calculated precisely.
In brief, the rate at which energy is used to
maintain an electric current varies directly with the resistance
involved, and with the square of the current intensity. This can be
expressed as P=I2R from E=IR of the Ohm’s law.
System loss as approved by the ERC has three
parts: technical, pilferage, and own use. Should consumers pay for
all three?
It’s not hard to justify the equal sharing by
all consumers of electricity of technical system loss. This is
inherent in the business of electric power generation and
distribution. It’s therefore a cost that everyone must pay to have
electrical power.
Pilferage is difficult, if not impossible, to
determine quantitatively. It therefore should be a loss that the
utility must bear alone, much like department stores hiring floor
detectives and installing surveillance cameras to discourage
shoplifting.
Own use is partly justified as a pass-on charge
to consumers. It takes energy to keep an electric current flowing
through resistance. This part can be calculated and should be shared
equally but the costs of lighting and cooling the offices of the
utility should not be borne by consumers.
Perhaps it’s time that the ERC hired some
physicists and economists for a more rational and science-based
regulatory regime.
opinion@manilatimes.net
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