Circuits: Is this Drawn Right?

[Saladsamurai]

Homework Statement

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

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

 

[cupid.callin]

Current do flow from - to +
What if you connect 6V and 3V batteries with +,+ connected and -,- connected?
what happens when you charge a cell?

 

[Saladsamurai]

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 So are we saying that in this particular circuit drawn, what ever the potential v_AB 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.

 

[gneill]

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.

 

[rwisz]

I understand your confusion about the polarity and current direction in this circuit. It is important to note that the direction of current flow is arbitrary and can be defined in either direction. In this circuit, the direction of current flow is shown in opposite directions for elements AB and FA, but this does not affect the overall functioning of the circuit. What matters is the relative polarity of the elements and how they are connected.

At Node A, the current is flowing from the positive terminal of element AB to the negative terminal of element FA. This is consistent with the direction of current flow in the rest of the circuit. As for the polarities of elements AB and FA, they are shown correctly in this diagram. Element AB is a resistor, which typically has a positive terminal at the top and a negative terminal at the bottom. Element FA is a voltage source, which usually has a positive terminal at the top and a negative terminal at the bottom. This is a common convention used in circuit diagrams.

As for Node C, it is important to note that it is not necessary for all elements in a circuit to have the same polarity. In this case, element CF is a capacitor, which has a positive terminal at the top and a negative terminal at the bottom. This is consistent with the polarity shown in the diagram.

In conclusion, while the direction of current flow may seem inconsistent in this circuit diagram, it does not affect the functioning of the circuit. The polarities of the elements are shown correctly and Node C is functioning as intended. I hope this explanation helps to clarify any confusion.