# Why the voltage is zero?

The question is asking to find ID1 and ID2 of the two ideal diodes in the circuit below: I solved it as follows: The correct solution is as follows: I would like to know where is my mistake. Also, why did he assume that the voltage at the anodes to be zero? why not 3 or 2 volts? How did he arrive to zero?  I know the question numbers are different,however, they are the most relevant to the question asked.

• Where did the original problem come from? Jan 10 at 14:23
• Just have to say, THIS is how you ask for help with a homework problem! Kudos for showing your work and your initial attempt. +1 for that. Jan 10 at 14:25
• As Andy says, it would be good to know where this "correct" solution comes from. Meanwhile, please don't "fix" your answer. Jan 10 at 14:30
• Questions to help you : What is the voltage over an ideal diode in forward bias? When you have that in mind, what is the voltage at the common junction of the diodes? Jan 10 at 14:32
• I guess it has something to do with the ground symbol (grown is 0 volt isn’t it?) Jan 10 at 14:36

Clearly, with a little effort, the solution that is given as correct is wrong. Just analyse the current through D1 with D2 disconnected: - The maximum current that can flow through D1 (assuming it is ideal with zero volt drop i.e. conditions that maximize current flow), is 6 volts / 43 kΩ = 0.1395 mA or 139.5 μA.

Given that the so-called correct solution is 409 μA, it is clearly miles off.

You cannot trust the so-called "correct solution".

I would like to know where is my mistake.

I would say (given the recent history of you posting questions that supposedly have "correct answer") that your mistake is in trusting these sites or books.

Also, why did he assume that the voltage at the anodes to be zero? why not 3 or 2 volts? How did he arrive to zero?

I've established that the "correct solution" source is faulty so there's no point trying to wonder what they did.

• Comments are not for extended discussion; this conversation has been moved to chat. Jan 11 at 16:12