Determining two diodes' currents

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The discussion revolves around determining the currents through two ideal diodes, D1 and D2, using circuit analysis methods. The user confirmed their calculations for three cases but struggled with the fourth, realizing they overlooked the effect of a 9V source on ID1, leading to an incorrect current value. Participants expressed confusion over the exercise's structure, noting that the circuit only has one viable state instead of four, suggesting a lack of clarity in the problem's design. They criticized the examiner for the poorly constructed question, which seemed to misrepresent how diodes function in the given context. Overall, the conversation highlights the challenges in analyzing diode circuits when assumptions about their states are unclear.
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Homework Statement



Assuming that D1 and D2 are ideals, determine ID1 and ID2 according to the table below.

123.png


Homework Equations



Circuit Analyzing methods (KVL, etc...)

The Attempt at a Solution



I've confirmed my solutions for the first three cases with final answers of the book I use and also with Multisim.

But for the fourth, while replacing the diodes with "on-switches", I used superposition to calculate the currents. I've ended up with ID1=ID1'+ID1''=12+9=21 mA, and ID2=-9 mA.

My answer is correct for ID2, but that not the case for ID1 (The answer should be 12 mA). Looks like the effect of the 9V source on ID1 was ignored. Why is that?
 
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Because there is no reason for it to have an effect - the diodes are basically replaced with short circuits.
The D1 short basically isolates the two halves from each other.
 
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My circuit analyzing again :S

Thanks :)
 
This is indeed a weird question. For the circuit shown, there are not 4 possible states, there is only one! For the options to make sense, either the "diodes" need to be SCRs or something similar (with gating arrangements not shown), or each diode needs an associated series switch---but in the schematic this is clearly missing.

I had no idea what to make of the exercise, not knowing what could be meant by a diode being off even though it may be forward-biased. :confused: :confused: :confused:

Now I can see what was intended, but this abomination reflects badly on the examiner. I'd grade him Epic Fail! :devil: :devil:
 
The exercise is on the "assumed states" method for analyzing diode circuits.
 
NascentOxygen said:
This is indeed a weird question. For the circuit shown, there are not 4 possible states, there is only one! For the options to make sense, either the "diodes" need to be SCRs or something similar (with gating arrangements not shown), or each diode needs an associated series switch---but in the schematic this is clearly missing.

I had no idea what to make of the exercise, not knowing what could be meant by a diode being off even though it may be forward-biased. :confused: :confused: :confused:

Now I can see what was intended, but this abomination reflects badly on the examiner. I'd grade him Epic Fail! :devil: :devil:

My thoughts exactly
 

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