Circuit problem- resistance, power, voltage

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Homework Help Overview

The discussion revolves around a circuit problem involving two resistors connected to a battery, where participants explore the internal resistance of the battery and the driving voltage based on given power values.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • Participants attempt to derive equations relating power, voltage, and resistance, exploring different approaches to calculate the internal resistance and voltage of the battery.

Discussion Status

Some participants have recalculated their results and shared differing answers, while others have confirmed the correctness of these calculations. There is an ongoing exploration of the relationships between the variables involved.

Contextual Notes

Participants are working under the constraints of the problem statement and are questioning their assumptions and calculations throughout the discussion.

mmoadi
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Homework Statement



We connect two resistors to a battery, once with the resistor of the resistance R1 = 2 Ω, and the second time the resistor of the resistance R2 = 0.5 Ω. In both cases the resistor uses up the power of 2W. What is the internal resistance of the battery? What is the driving voltage of the battery?

Homework Equations



P= V*I
V= R*I
P= R*I²
P= V²/ R

The Attempt at a Solution



- Now I derivate three general equations:

1) V(0)= R(1)I(1) + R(0)I(1)
2) I(1)= V(0)/ (R(1) + R(0))
3) I(2)= V(0)/ (R(2) + R(0))

- Now I plugged these three equations in the power formula and got:

P= R(1)I(1)²= R(1)*[V(0)²/ (R(1) + R(0))²]
V(0)²= [P*(R(1) + R(0))²]/ R(1)

P= R(2)I(2)²= R(2)*[V(0)²/ (R(2) + R(0))²]

P= R(2)* [(P*(R(1) + R(0))²)/ (R(1)* (R(2) + R(0))²)]
1= [R(2)/R(1)]*[ (R(1) + R(0))²)/ (R(2) + R(0))²)]
R(2)/R(1)= (R(1) + R(0))²)/ (R(2) + R(0))²)
sqrt(R(2)/R(1))= (R(1) + R(0))/ (R(2) + R(0))
sqrt(R(2)/R(1))* (R(2) + R(0))= R(1) + R(0)
R(0)*(sqrt(R(2)/R(1))) – 1)= R(1) – ((sqrt(R(2)/R(1)))*R(2))
R(0)= [R(1) – ((sqrt(R(2)/R(1)))*R(2))]/ [sqrt(R(2)/R(1))]
R(0)= 1/3 Ω

V(0)²= [P*(R(1) + R(0))²]/ R(1)
V(0)²= 2.33 V

Are my calculations correct?
Thank you for helping!:smile:
 
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I am getting different answer.
P= R(1)*[V(0)²/ (R(1) + R(0))²] = R(2)*[V(0)²/ (R(2) + R(0))²]
Cancel V(0)^2 from both and rearrange the terms. You get
R(1)/R(2) = [R(1) + R(0)]^2/[R(2) + R(0)]^2
Substitute the values of R(1) and R(2) and solve for R(0).
 
OK, I rewrote my equations and recalculated and this are my new results:

R(0)= 1 Ω
V(0)= 3 V

Are my calculations correct?

Thank you for helping!:smile:
 
Yes. Your calculations are correct.
 
Thank you for reviewing and all the help!:smile:
 

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