Get Current and Voltage with a Circuit with Diodes

[roinujo1]

Homework Statement

Find the V and I in the circuit shown below:

Homework Equations

• D_{1 or 2} is off=short circuit
• D_{1 or 2} is on=open circuit

The Attempt at a Solution

So, my confusion lies with deciding the on and offs of D1 and D2 . My assumption is that both of them are on and that is due to them in forward bias. However, when I looked online, D2 was off and D1 was on. Based on how the current is going into D2, how is D2 off?

Any help is much appreciated!

 

[berkeman]

Homework Statement

Find the V and I in the circuit shown below:

View attachment 107760

Homework Equations

• D_{1 or 2} is off=short circuit
• D_{1 or 2} is on=open circuit

The Attempt at a Solution

So, my confusion lies with deciding the on and offs of D1 and D2 . My assumption is that both of them are on and that is due to them in forward bias. However, when I looked online, D2 was off and D1 was on. Based on how the current is going into D2, how is D2 off?

Any help is much appreciated!

Your Relevant Equations are backwards, BTW. On=short and Off=open for diodes.

What is the typical forward voltage for a silicon diode? What is the anode voltage for D2 if it is off? And if D2 were on, what would that do to the Anode voltage?

 

[roinujo1]

Your Relevant Equations are backwards, BTW. On=short and Off=open for diodes.

What is the typical forward voltage for a silicon diode? What is the anode voltage for D2 if it is off? And if D2 were on, what would that do to the Anode voltage?

Thank you for the response!

Aww, I'm sorry. Yeah it does look like they are bakwards (was in a rush). Thank you for that.

Im sorry, but what do you mean by anode voltage? My assumption was that d2 was forward positive because:

 

[roinujo1]

Basically, I think I want to know why D1 and D2 both can't be on.

 

[gneill]

Basically, I think I want to know why D1 and D2 both can't be on.

Look for circuit behavior contradiction(s) if you assume that both are on. For a quick evaluation, assume that the diodes are ideal (no forward voltage or resistance). What would be the potential V on your diagram? Determine all the currents through the components (should be simple if you know the potential drops on the resistors and KCL for the junctions). What do you get?