Series circuit answers correct?

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Homework Help Overview

The discussion revolves around a series circuit involving three batteries and resistors, with specific values provided for voltage and one resistor. The original poster seeks to confirm their calculations regarding current and resistance values.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants question the validity of the original poster's calculations, particularly the determination of current through the resistors. There is a request for clarification on how the original poster arrived at their results, especially regarding the use of total voltage.

Discussion Status

Some participants have provided guidance on the need for a circuit diagram and emphasized the importance of correctly identifying the voltage across each resistor. There is an ongoing exploration of how to apply Ohm's law to find the correct current through R3.

Contextual Notes

Participants note the absence of values for R1 and R2, which may affect the overall analysis. The original poster's approach of using total voltage for calculations is also under scrutiny.

confused12345
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Homework Statement


3 batteries: Vt= 40v+20v+10v = 70v
R1= unknown
R2= Unknown
R3= 10 ohm
I= unkown
The ones which I am looking for are:
I3=___
I1=___
V1= ___
R1=___
R2=___



Homework Equations


V=IR
I=V/R
R=V/I


The Attempt at a Solution


I3= 7a
I1= 7a
V1=70v
R1= 10 ohm
R2= 10 ohm
Diagram:

Is this correct?
 

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Hard to say. Strike that--impossible to say. Need a circuit diagram, please.
 
There seems to be some problems with your results. You'll have to give some details on how you arrived at your answers. How did you determine i3 to be 7A?
 
I used the equation I=V/R
70/10 ohm <--- since that was the only resistance already given?
 
I see. Well, presuming that the 70V you've quoted is the sum of the voltages shown for the battery and the voltages across R2 and R3, then that 70V is NOT across R3. It's the potential across R1, which you don't yet have a value for.

Your figure shows a voltage across R3. Why don't you use that voltage and that resistance to determine the current?
 
So if I use
I=V/R
=20/10
=2a
That is the correct current? I was using the totals to find I the first time.
 
confused12345 said:
So if I use
I=V/R
=20/10
=2a
That is the correct current? I was using the totals to find I the first time.

Yes, that is the correct current. It is a direct consequence of Ohm's law applied to R3 where you are given both the value of the resistance and the voltage across it.
 

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