Engineering Solving a Circuit with Diodes: Find V Across Resistor

[Ry122]

Homework Statement

http://img832.imageshack.us/img832/6302/20285200.jpg

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Homework Equations

The Attempt at a Solution

I'm unsure where to begin with this.
I need to find the value V across the resistor and I'm unsure how.
What effect do the diodes have in a circuit that's set up in this way?

 

[CEL]

Both diodes are forward biased.
If they are ideal, you can replace them with short circuits. If not, you can replace them by voltage sources of 0.6 V.

 

[berkeman]

Homework Statement

http://img832.imageshack.us/img832/6302/20285200.jpg

Uploaded with ImageShack.us

Homework Equations

The Attempt at a Solution

I'm unsure where to begin with this.
I need to find the value V across the resistor and I'm unsure how.
What effect do the diodes have in a circuit that's set up in this way?

Start by ignoring the diodes, and solve for the two separate resistor divider voltages. What do you get? Now if you put in one diode at a time, what happens? And then with both of them in at once?

Both diodes are forward biased.

I'm not sure that is true...

 

[Ry122]

How come when solving these circuits you're supposed to make assumptions about which ones might be on and which ones are off, and then check to see if you're right?

Why can't you just look at the voltages on either side of the diodes and see whether the cathode or anode side is greater?

 

[uart]

Why can't you just look at the voltages on either side of the diodes and see whether the cathode or anode side is greater?

You can if there's just one diode, but in general the A-K polarity of a particular diode will depend on the state (conducting / non conducting) of all the other diodes in the circuit. Your original question above is a good example of this.