can you help me how to determine if it's forward or reverse biased.

 

can you help me how to determine if it's forward or reverse biased.

Find the voltage at the node located between the two resistors.

If voltage is positive, the diode is reverse biased.

If voltage is negative, the diode is forward biased.

 

can you teach me how to do that? please bear with me I'm just starting to learn this stuff.

 

can you teach me how to do that? please bear with me I'm just starting to learn this stuff.

Read this: http://www.ecircuitcenter.com/SpiceTopics/Non-Linear Analysis/Non-Linear Analysis.htm

 

Can you use Kirchoffs Voltage Law? (halfway down the page)

 

The general approach is to make an assumption about the state of the diode and then analyze the circuit under that assumption to see if the circuit's behavior is consistent with that assumption being true. If it is, you picked right and are done. If it is not, you picked wrong and just have to go back, make the other assumption, and analyze the circuit under that assumption (and be sure that the result is consistent with the new assumption being true).

With practice, you will get so that you can usually make the correct assumption the first time. Until then, just make you best guess and go for it. When you guess wrong, take a moment to see if you can spot anything that would have provided hints as to why the other assumption was the correct one -- sometimes you can and sometimes you can't.

When it isn't obvious that the diode is probably forward biased, it is generally (not always) easier to analyze the circuit assuming the diode is reverse biased since it removes that branch from the circuit. Now you just analyze the circuit and find the voltage across where the diode was and see if that voltage is consistent with the diode being reverse biased (or at least not forward biased beyond whatever turn-on voltage you are using for your model).