Circuit with Four Resistors and Two Switches

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Homework Help Overview

The discussion revolves around a circuit problem involving four resistors connected to a battery, with two switches affecting the circuit's configuration. The original poster is trying to determine the potential difference between two points in the circuit when one switch is closed and the other is open.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to calculate the total resistance and current in the circuit, but expresses uncertainty about their approach. Other participants suggest analyzing the circuit with the second switch closed and applying Kirchhoff's Current Law (KCL) at specific nodes.

Discussion Status

Participants are actively engaging with the problem, with some providing guidance on how to approach the analysis of the circuit. There is a focus on understanding the implications of closing the second switch and how it affects the potential at certain nodes.

Contextual Notes

There is a mention of a missing image that may be crucial for visualizing the circuit setup. The original poster's initial confusion about the starting point in the circuit is also noted.

Jake Russell
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Homework Statement


Four resistors connected to a battery are shown in the figure (at bottom). The switch S2 is closed and switch S2 is left open. What is the magnitude of the potential difference Vcd

Homework Equations


Rp= Σ(1/Ri)-1

Rs = ∑Ri

V = IR

The Attempt at a Solution


Seeing as c and d aren't directly connected since S2 is open, I attempted to find the total resistance using the two resistance equations above and from that find the total current. After that, I divided the total current by two since the total resistance on both sides are the same, and multiplied that by the total of the top resistance. Next I added the current multiplied by the bottom left resistor and subtracted the current multiplied by the bottom right resistor, but I don't think this is correct.
upload_2016-3-2_18-18-20.png
 
Last edited:
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Hi Jake Russell, Welcome to Physics Forums!

The mage that you tried to attach isn't viewable. Can you upload it again?
 
I ended up figuring out this question (I wasn't starting at a and not c), but I have another one. How would I find the current through the second switch when it is closed?
 
With switch S2 closed can you find the potential at node cd? (Since S2 joins c and d together, they become a single node).

Knowing the potentials at a,b, and c, can you write a KCL equation at location c?
 
Work out the voltage drop across each resistor (easy) then calculate the current in each resistor and mark it on the diagram. Apply KCL at either node c or d.

Edit: cross posted with gneill.
 

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