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Sources of Electricity
10 questions By Tony R. Kuphaldt
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Question 4 of 10
There is a fundamental Law in physics known as the Law of Energy Conservation. This law states that energy can neither be created nor destroyed, merely transformed from one form to another.
In regard to this Law, is it possible to make an electrical battery that lasts forever, and never becomes exhausted? Explain why or why not.
Reveal answerAccording to the Law of Energy Conservation, it is not possible to make a battery that lasts forever.
Notes:This question may lead into a discussion on perpetual motion machines, a subject that seems to be perpetual itself in the popular interest.
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Question 5 of 10
The mathematical equivalence between watts and horsepower is approximately 746:1. Given this equivalency, how many watts of electrical energy may theoretically be produced by a generator, if turned by an engine rated at 50 horsepower?
Reveal answer37.3 kW of electrical power.
Notes:Unit conversion problems are handled most easily by using “unity fractions” comprised of a quotient of two different numerical quantities having the same physical value. For instance:
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Question 6 of 10
Suppose a person decides to attach an electrical generator to their exercise bicycle, so as to do something useful with their “pedal power” while they exercise. The first time this person uses their bicycle generator, the electricity is used to power a single 60-watt light bulb. However, the next time this person uses their bicycle generator, a second 60-watt light bulb is connected to the generator, for a total load of 120 watts.
When pedaling with the additional load, the person notices the bicycle is much more difficult to pedal than before. It takes greater force on the pedals to maintain the same speed as before, when there was only a single 60-watt light bulb to power. What would you say to this person if they asked you, the electricity expert, to explain why the bicycle is more difficult to pedal with the additional light bulb connected?
Reveal answerI won’t give you the answer directly, but here is a hint: the Law of Energy Conservation.
Notes:This phenomenon is more easily understood when experienced directly. If you happen to have a hand-powered generator available for a classroom demonstration, help your students set it up to demonstrate this principle.
An excellent topic of discussion related to this question is the effect that using more electrical power has on the generators at power plants (hydroelectric, nuclear, coal-fired, etc.). What would happen at the power plants supplying electricity to the nation’s electrical “grid” if everyone simultaneously turned on all their electrical loads at home?
