Direction of current in the figure?

[ehabmozart]

Direction of current in the figure??

Homework Statement

What must the emf in the figure be in order for the current through the 7.00-ohm resistor to be 1.76A? Each emf source has negligible internal resistance. Figure

http://i239.photobucket.com/albums/ff92/anakris_24/yf_Figure_26_51.jpg

Homework Equations

Kirrchoff's Laws

The Attempt at a Solution

I know well how to use the laws but my problem here is in determining the direction of current through the 7Ω resistor. Is it up or down and why? ... In the manual it say it goes down due to polarity of the battery.. But it can actually go out of battery 1(left) and battery two?

 

[gneill]

Try applying superposition. What direction does the current flow through the 7 Ω resistor due to each source when taken individually?

 

[CWatters]

In the manual it say it goes down due to polarity of the battery.. But it can actually go out of battery 1(left) and battery two?

I don't understand your explanation. Even if the current flows out of the 24V battery into the ε battery the top end of the 7R will still be +ve wrt the bottom end.

If ε is +ve then I can't see how the current can ever flow upwards through the 7R.

Edit: It would be bad practice to show ε as -ve with the battery drawn that way around. It would be ok to show a voltage source with the arrow pointing upwards and ε marked as -ve but that's not what you have here.

 

[CWatters]

How about solving it twice. Once assuming the current flow down through the 7R and one assuming it flow up through the 7R. What do you get?

 

[Nickie]

I would begin by analyzing the circuit and determining the possible paths for current flow. It appears that there are two possible paths for current to flow through the 7Ω resistor - one from the positive terminal of battery 1 through the resistor and back to the negative terminal of battery 1, and the other from the positive terminal of battery 2 through the resistor and back to the negative terminal of battery 2.

Based on the information provided, it is not possible to determine the exact direction of current through the 7Ω resistor. This is because the circuit is incomplete and does not show the connections of the batteries to the rest of the circuit. Without this information, we cannot determine the polarity of the batteries and therefore cannot determine the direction of current flow.

In order to solve the problem and determine the emf needed for a current of 1.76A through the 7Ω resistor, we would need to know the complete circuit and use Kirchhoff's laws to analyze the circuit and solve for the emf. Additionally, we would need to know the internal resistance of the batteries in order to calculate the total resistance in the circuit and use Ohm's law to solve for the emf.

In summary, without more information, it is not possible to determine the direction of current in the figure. As scientists, it is important to have complete and accurate information in order to make accurate conclusions and solve problems.