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Simple circuit analysis w/ voltage sources - MasteringPhysics wrong?

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  • #1
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Homework Statement


We are given a simple circuit with 4 resistors, a known voltage source, and an unknown voltage source. The photo is below in my solution attempt.


Homework Equations


V=IR, R(parallel)=(1/R1+1/R2)^-1


The Attempt at a Solution


I found the voltage drop over the given resistor, then used that voltage to find the current through the other resistor in parallel, which gave me the total current through the circuit.

http://imgur.com/HtJootR

My problem is I am pretty sure MasteringPhysics is wrong here. I included all of my work finding my answer, and then tested their answer to show that it is wrong. I am confident in my work but was hoping you could look it over before I go make a dodo of myself to my instructor.
 

Answers and Replies

  • #2
gneill
Mentor
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2,716


Homework Statement


We are given a simple circuit with 4 resistors, a known voltage source, and an unknown voltage source. The photo is below in my solution attempt.


Homework Equations


V=IR, R(parallel)=(1/R1+1/R2)^-1


The Attempt at a Solution


I found the voltage drop over the given resistor, then used that voltage to find the current through the other resistor in parallel, which gave me the total current through the circuit.

http://imgur.com/HtJootR

My problem is I am pretty sure MasteringPhysics is wrong here. I included all of my work finding my answer, and then tested their answer to show that it is wrong. I am confident in my work but was hoping you could look it over before I go make a dodo of myself to my instructor.
Their answers look fine to me.

Write out the voltage drops across each resistor. You know that they will potential drops in the direction of current flow, and that current flow can be either clockwise or counterclockwise. Perform a "KVL walk" around the loop assuming that the current flows in one direction and solve for the required Vba. Then do the same again assuming the current is flowing in the other direction.

By the way, that's a 1.0Ω resistor on the bottom, not a 1kΩ resistor.
 
  • #3
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By the way, that's a 1.0Ω resistor on the bottom, not a 1kΩ resistor.
Consarn it. I think that's the source of my problems. I didn't notice it had different units to the rest of them.
 

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