Hi, I have a question about DIODES that may not be covered in VCE Physics.
If I have 2 diodes arranged in series, both having a switch-on voltage of 0.7V but my supply voltage is strictly within the range of (0.7, 1.4) Volts (exclusive), what happens?
I remember my teacher from last year saying that electrons are already present in the wire and that they do not "begin flowing" from the negative terminal of the battery to the positive terminal. If this is the case, the closest one to the battery isn't necessarily the answer. He also explained P-N junctions in semi-conductors to us at one stage, which may be involved in the answer.
I asked my teacher last year during a Prac Period and he replied simply with a "you should try and find out" but I never actually got around to seeing what happens. I have a couple of speculations as to what happens:
1. Either Diode 1 or Diode 2 turn on, but the other remains off. The battery supplies its total voltage, but since not enough is supplied to turn both on, one takes 0.7 and the other takes the remaining and thus does not reach the required switch-on voltage. Perhaps each time this happens, it is a random process as to which one turns on?
2. Neither turn on, but this is probably the least logical answer. Imagine a Diode and Ohmic Resistor arranged in series; the Diode will always use 0.7 V, regardless of how the series circuit is arranged, given that the supply voltage >0.7V. Therefore, shouldn't speculation 1. be more feasible?
3. When I attended the ATARNotes Physics Headstart Lecture at RMIT during the holidays, I asked Alwin the presenter this question. He explained that both would be on, but would be dim. Both would receive a voltage in-between 0 and the switch-on voltage of 0.7. Since in reality, the "boundary" between "on" and "off" is not as clear-cut as 0.7V, there is a "zone" where they are "on." Therefore, both are on but are dim.
However, if the 3rd option is true, if I were to supply 0.6 V to a circuit containing only 1 diode, shouldn't it be "on"? Shouldn't each coulomb of charge expend 0.6 Joules of energy to cross the P-N junction?
I tried to find an answer to this question on Google, but the circumstance might have been too specific to type into Google and couldn't find a suitable solution