The practical benefit of active devices is their amplifying ability. Whether the device in question be voltage-controlled or current-controlled, the amount of power required of the controlling signal is typically far less than the amount of power available in the controlled current.
In other words, an active device doesn’t just allow electricity to control electricity; it allows a small amount of electricity to control a large amount of electricity. Because of this disparity between controlling and controlled powers, active devices may be employed to govern a large amount of power (controlled) by the application of a small amount of power (controlling). This behavior is known as amplification.
It is a fundamental rule of physics that energy can neither be created nor destroyed. Stated formally, this rule is known as the Law of Conservation of Energy, and no exceptions to it have been discovered to date.
If this Law is true – and an overwhelming mass of experimental data suggests that it is – then it is impossible to build a device capable of taking a small amount of energy and magically transforming it into a large amount of energy.
All machines, electric and electronic circuits included, have an upper efficiency limit of 100 percent. At best, power out
equals power in as in Figure 1.
Usually, machines fail even to meet this limit, losing some of their input energy in the form of heat which is radiated into surrounding space and therefore not part of the output energy stream. (Figure 2) Many people have attempted, without success, to design and build machines that output more power than they take in.
Not only would such a perpetual motion machine prove that the Law of Conservation of Energy was not a Law after all, but it would usher in a technological revolution such as the world has never seen, for it could power itself in a circular loop and generate excess power for “free”.
|Title:||Lessons In Electric Circuits, Volume III – Semiconductors – Tony R. Kuphaldt|
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