The true meaning of voltage drop

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In CE amplifiers, an increase in the transistor's hfe leads to higher emitter current (Ie) and a corresponding increase in voltage across the emitter resistor (RE), making the emitter more positive. This phenomenon is explained by the negative feedback mechanism, where any rise in collector current (Ic) or emitter current (Ie) causes an increase in voltage drop across RE, thus stabilizing the circuit. The term "voltage drop" refers to the potential difference across a resistor, which is a result of current flow rather than the cause of it. Understanding this relationship emphasizes that voltage is necessary to drive current through a resistor, aligning with Ohm's Law (V=IR). Ultimately, voltage drop can be viewed as the energy required to maintain current flow through resistive elements in a circuit.
  • #31
jim hardy said:
So hydraulic analogy is useful to get your brain accustomed to working circuits "in your head" .
old jim

Yes - I fully agree.
As an interesting exercise, one could try to explain the amplifying properties of a transistor using the hydraulic analogy - in particular, if it seems to be possible that a tiny flow of water is able to control (with gain !) the water flow of a much larger river.
 
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  • #32
LvW said:
if it seems to be possible that a tiny flow of water is able to control (with gain !) the water flow of a much larger river.
Pressure actuated valve on a much larger flow pipe? (Ah, this would be a FET)
 
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  • #33
Voltage is work done per unit charge , therefore when we say voltage drop work is done between the resistor ie really a energy loss ,and it is physical quantity
 
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  • #34
You have to be careful using purely conceptual thinking with physics. Sometimes things behave in a way that's not intuitive. On the the other hand, the math does not always clarify dependencies such as the fact voltage has to be present before current will flow. Usually you need to understand the math first to understand the behavior conceptually. We use the term Voltage drop in a practical catch all manner, but the term fails to provide a sense of what's really going on there. The outward appearance is a voltage differential between one node and another, but there's physical behaviors taken for granted that result in those observable measurements.
 
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  • #35
CraigHB said:
We use the term Voltage drop in a practical catch all manner, but the term fails to provide a sense of what's really going on there.

"Voltage drop" is almost slang for voltage across something that is removing energy from a circuit, ie a load such as a motor or lamp
curiously
it's rare to hear the converse term "Voltage rise" describing voltage across something that deposits energy ie a source such as a battery or power supply.
 
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  • #36
Thanks everyone, your help is very helpful!
 

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