Discussion in 'Homework Help' started by NichA, Jun 10, 2007.

1. ### NichA Thread Starter Member

Jun 10, 2007
13
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I had to calculate the current i in this circuit. (Note: There are other values included that I didn't show as they are not needed)

So I did a bunch of math calculating i to be -20mA and then when I read the answer in the answer key it just said:

i=0 because no current can exist in a single conductor that connects two parts of a circuit.

I don't understand why no current can exist here like the answer says...?

I guess one explanation could be that there is no voltage difference between the two points but couldn't that current source still push current through?

2. ### NichA Thread Starter Member

Jun 10, 2007
13
0
I mean, if there is no current flowing between those two parts then what is the point of that connection? Wouldn't it all work the same if that wire was gone?

3. ### hgmjr Moderator

Jan 28, 2005
9,030
214
This connection is shown in the model to indicate that these two circuits have a commom point of reference.

hgmjr

4. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
657
Current flows in a loop, i.e., it must have a return path. That circuit has no path for thr current to return to the source. The wire has no current, but it does serve to keep both sides at the same potential, which might be important when the circuit is included in a larger system. This particular circuit is one way of modeling the small-signal behavior of a bipolar transistor., so the connection is important.

5. ### cumesoftware Senior Member

Apr 27, 2007
1,330
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The point is to have the same potential reference.

6. ### Distort10n Active Member

Dec 25, 2006
429
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What book is this from? This circuit looks familiar. Then again, don't they all?

7. ### Ron H AAC Fanatic!

Apr 14, 2005
7,050
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As I mentioned above, it's a small-signal bipolar transistor model (H-parameter).