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this is a hand-wavy kind of answer that will probably get down-voted. the collector-base junction is normally reverse-biased in a circuit where a BJT is used as a current amplifier. because it's reverse-biased the material on both sides of the junction are then depleted of charge carriers for the same reason a reverse-biased diode is. then, without charge ...

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Piezoelectricity has been found in liquid crystals too, see for ex. see RB Meyer, Physical Review Letters 22, 918 (1969). To show piezoelectricity, a material needs some degree of anisotropy; thus it would hardly be possible to find piezoelectricity in liquids, which are pretty isotropic.

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Piezoelectricity, at least in the usual meaning of the word, arises when you deform a material that does not have a centre of symmetry i.e. there is no inversion symmetry. Liquids are amorphous and therefore (on average) isotropic. This means they are inversionally symmetric (about any point in fact) and therefore will not generate piezoelectricity when ...

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The concept of a photon comes from quantum field theory, but the radiation from your remote control is well in the classical regime, so we need to figure out how to go from the quantum field theory to the classical field theory. Now, the way we do that is by forming so called minimum uncertainty states. There's a Heisenberg uncertainty principle for fields ...

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Most likely, your garage door opener operates at a frequency of 315 MHz. Multiplying by Planck's constant, that means each photon has energy of about $2\times 10^{-25}$ joules. Most likely, your garage door opener operates at about $1/10$ of a watt (or less, per comments below). So each second, it emits 1/10 of a joules of energy. That's \$(2/10) ...

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I think you're just asking for some clarification on terminology. Imagine a circuit which consists of only a resistor (passive component) connected across a battery (an active component). The end of the resistor connected to the battery's positive terminal will be it's positive end. In the conventional current model, current flows out of the battery's ...

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The second paragraph from this IEEE reference follows: Every electrical engineer learns early of the two Kirchhoff laws, but not very many realize that they were published while he was still a student. The publication is {(vom Studiosus) Kirchhoff, “Ueber den Durchgang eines elektrischen Stromes durch eine Ebene, insbesonere durch eine kreisförmige,” ...

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