Draw an electric circuit potential graph

[EMEE_]

Homework Statement

Draw an electric circuit potential graph and find out the potential difference between points B and C. The two resistors have equal values.

Relevant Equations

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Hi.

I have physics homework that I don't understand. Hopefully, someone here can give me some advice. So, the homework goes like this:

Draw an electric circuit potential graph and find out the potential difference between points B and C. The two resistors have equal values.

Believe me or not, I've been trying to solve this for days.
I know that the direction of the circuit flows from the positive pole to the negative pole. I have already calculated the voltage drops of the resistors by using the given voltages. (So, R1 & R2). ---> 24V-10V-8V = 6V : 2 --> 3V / per resistor. Have I done anything right? Could somebody please tell me what to do next and how? And with what formulas? I can draw the potential graph but I don't know how to find the right values.Thanks.

 

[EMEE_]

I also know that the voltage of A is 0V.

 

[haruspex]

So, R1 & R2). ---> 24V-10V-8V = 6V : 2 --> 3V / per resistor.

Since the resistors are equal and the same current flows through both, the voltage drop is the same across each. So, yes, that works, but it would not work more generally.

Next step is to consider which way the current flows. That will tell you which way the voltage changes by 3V at each resistor.

In future, please use more informative titles for threads.

 

[EMEE_]

Since the resistors are equal and the same current flows through both, the voltage drop is the same across each. So, yes, that works, but it would not work more generally.

Next step is to consider which way the current flows. That will tell you which way the voltage changes by 3V at each resistor.

In future, please use more informative titles for threads.

The current flows clockwise, doesn't it?

When moving in the direction of the electric current, the potential increases in the batteries but decreases in the resistors. Am I right?

 

[EMEE_]

But I'm just hesitating what formulas to use. How can I calculate the voltages right?

 

[collinsmark]

The current flows clockwise, doesn't it?

When moving in the direction of the electric current, the potential increases in the batteries but decreases in the resistors. Am I right?

You may pick the direction of the current flow arbitrarily. The important point here is that once you pick a direction you need to be consistent with it.

Once you pick the direction for your current, solve for [itex] iR [/itex]. You don't have enough information to solve for [itex] i [/itex] or [itex] R [/itex] individually. But you do have enough information to solve for the quantity "[itex] iR [/itex]" as a whole. [Edit: Keep in mind [itex] iR [/itex] might be positive or it might be negative depending on which direction you choose for the current.]

Remember when I said that you may arbitrarily choose the direction of current as long as you're consistent? Well, here is where you need to be consistent. You now can put the voltage drop across each resistor paying careful attention to get the polarity correct, i.e, paying carful attention to put the "+" sign and the "-" sign on the correct terminals of a given resistor.

Remember, it's called "voltage drop." As the current flows through the resistor, it starts on the "+" side and ends on the "-" side, indicating that the potential has decreased (i.e., "dropped") on the minus side of the resistor compared to the "+" side, by the amount [itex] iR [/itex].

Optionally, if you choose to, you can change the polarity of [itex] IR [/itex] from positive to negative or vice versa, and then correspondingly change each of the resistors' polarities accordingly (change the "+" terminals to "-" and the "-" terminals to "+". It should give you the same final answer either way. But you don't need to do this step. It's completely optional.

From there just add up the potentials from C to B paying carful attention to the polarity of each component.