# circuit notation

Discussion in 'Homework Help' started by keltix, Jan 10, 2010.

1. ### keltix Thread Starter New Member

Jan 10, 2010
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Last edited: Jan 10, 2010

Apr 26, 2005
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3. ### beenthere Retired Moderator

Apr 20, 2004
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What notation is strange - resistors, diodes, or the clearly backwards direction of current? We seem to have a permanent stream of conventional vs. actual current flow direction questions.

4. ### keltix Thread Starter New Member

Jan 10, 2010
6
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just that the circuit is not connected..

and i think i had it wrong: the first one would be equivalent to a 2V battery.....

5. ### beenthere Retired Moderator

Apr 20, 2004
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The arrows at the ends of the line mean there is an explicit connection to a voltage source as stated.

6. ### keltix Thread Starter New Member

Jan 10, 2010
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what changes if the resistor or the diode comes first?

7. ### scythe Active Member

Mar 23, 2009
49
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Hey there Keltix, I'm not going to do your homework for you, but it IS helpful to have a good example to go off of...

... so here it is.

I think the equivalent circuit is the one I've posted below. You know that the bottom is at -1v potential, so you just use the 0.7v model for the diode (this models the voltage necessary for the diode to be forward biased-- without this you have an open circuit that does not conduct! ), and add the 0.7v drop to figure out what Vout is. Once that's done, you can find the current going through your resistor, and because Vout is an open circuit, you know that the same current has to be going through your diode, and you have thus solved I.

If I'm wrong, somebody correct me, but I think that's right...

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8. ### keltix Thread Starter New Member

Jan 10, 2010
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ok, so in scythe's diagram... that would mean the voltage of the battery is 2V, right????

9. ### SgtWookie Expert

Jul 17, 2007
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In the leftmost circuit, the total potential is 2 Volts across the resistor and diode.

What do you think the voltage will measure across the diode?

10. ### SgtWookie Expert

Jul 17, 2007
22,183
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Ask yourself, "What is the maximum possible current that could flow from the most positive source to the most negative source?" Keep in mind that the 130 Ohm resistor will limit the current flow, if nothing else will.

11. ### keltix Thread Starter New Member

Jan 10, 2010
6
0
approximate at .7V?

12. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Even without that in the equation.

What's the maximum current that will flow across a 130 Ohm resistor when 2v is placed across it?

(The 130 Ohms is a big hint though).