Is there a circuit element which dissipates energy but does not act as a resistor?

-

My answer to SE EE question Is there a circuit element which dissipates energy but does not act as a resistor? [closed]

Many interesting psychological phenomena can be observed in StackExchange. One of them is the closing of interesting, non-standard and original questions by people having more limited thinking. Such people have the ability to quickly unite into something resembling Russian "NKVD troika". As a result of this filtering, the platform is full of monotonous and boring questions. Here is another example...

My answer

OP: ... is there an energy sink which does not alter the properties of the circuit?

Yes, there is such a "sink"; its name is "transimpedance amplifier" - Fig. 1a. In this conceptual circuit diagram, the op-amp output is represented by the variable voltage sourve VOA.

Fig. 1. Transimpedance amplifier - a conceptual circuit diagram (circled in blue).

It consists of two elements in series - a resistor R2 and a variable voltage source (a properly supplied op-amp) that copies the voltage drop VR2 across the resistor and adds it to VR2. As a result, the voltage between the two circuit terminals (op-amp inputs) is zero (VR2 - VOA = VR2 - VR2 = 0)... and the circuit (circled in blue) behaves just as a "piece of wire" - Fig. 1b.

The resistor R2 dissipates power but the op-amp adds the same power; so "this sink does not alter the properties of the circuit" (VIN, R1)... as you want. The current is I = VIN/R1 whether or not this "sink" is inserted...

My comments

  1. Original question... that provokes original answers...
  2. And where does this power (consumed by the source) go in the end?
  3. I think that whether it is ideal or real is not so important (in the latter case, only part of the energy will be dissipated in its internal resistance). The question is fundamental and it is more important whether the source is reversible - for example, a motor (dynamo), speaker (microphone)... and a special case is a rechargeable battery. In these cases, the energy consumed will be converted into the appropriate form. I wonder what happens when the source is not reversible. For example, what will happen if we connect an ordinary battery in series and in an opposite direction to the main one?

Comments

Post a Comment