[SOLVED] what is the voltage across the diode "considering the complete model"

[MSAKARIM]

Is this solution right?

 

[FvM]

Solution is wrong. About 0.86 mA If.

No "complete model" is given in your post.

 

[MSAKARIM]

I mean when I replaced the diode with ( small resistance rd'=10 and battery of=0.7v). The diode is forward biased

Solution is wrong. About 0.86 mA If.

No "complete model" is given in your post.

 

[FvM]

That's all correct, but the current is wrong. You ignore the current from the +10V source.

 

[aminpix]

You can replace the diode with a 10 ohm resistor and a 0.7 volt power supply. Then a equation should be solved to find the Voltage across the diode which is:
(-690) / 998 = -0.69138276553

 

[LvW]

You can replace the diode with a 10 ohm resistor and a 0.7 volt power supply. Then a equation should be solved to find the Voltage across the diode which is:
(-690) / 998 = -0.69138276553

Two rough assumptions (without explanation) - and a result with a pico-volts accuracy.´?
No - without any further information, we have no other chance than to ASSUME 0.7V across the diode and find the current through the diode (method of node voltages): Id=0.86mA.

 

[crutschow]

You can calculate the Thevenin equivalent of the circuit without the diode.
From that you can calculate the current through the diode when it is connected.

 

[FvM]

No - without any further information, we have no other chance than to ASSUME 0.7V across the diode and find the current through the diode (method of node voltages): Id=0.86mA.

Yes. The OP is apparently assuming 0.7V with 10 ohm series resistance as model, without stating this explicitly or even a substantiation. In this case, the exact current would be
4.3 V/5.01 kOhm = 0.858 mA, negligible difference to the simplified calculation without series resistance. Post #5 is wrong in any case.