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Circuits: Is this Drawn Right?

  • #1
3,003
2

Homework Statement



Here is a figure from my text and I am wondering if this is a mistake:

Screenshot2011-01-30at95552PM.png



Now, what is going on at Node A? I was always shown that the current flows from + to - through an element of a circuit. When you look at the elements connected to A, element AB has the current flowing from + to - and the element FA has it from - to +. More importantly, how can elements AB and FA have the polarities shown?

I won't even get into Node C until I figure out what is happening at A.

Please help :redface:
 

Answers and Replies

  • #2
1,137
0
Current do flow from - to +
What if you connect 6V and 3V batteries with +,+ connected and -,- connected?
what happens when you charge a cell?
 
  • #3
3,003
2
Current do flow from - to +
What if you connect 6V and 3V batteries with +,+ connected and -,- connected?
what happens when you charge a cell?
Hi c.c :smile: So are we saying that in this particular circuit drawn, what ever the potential vAB is, it must be large enough to draw the current across the element FA. That is, by itself FA would *like* to have current flowing from + to -. But since it is in the presence of whatever element AB is, its current is *forced* back through it.
 
  • #4
gneill
Mentor
20,793
2,773
The current labels are just that: labels. They are variables without pre-assigned value (to be determined). When the values are determined by solving the appropriate equations, some may turn out to be negative, indicating that the assumed directions were not in accord with the true situation.

You shouldn't let this worry you. Variables are, well, variable after all.
 

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