Resistance and DC circuit question

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Homework Help Overview

The discussion revolves around a problem involving three 100 Ω resistors connected in a circuit, focusing on calculating the maximum potential difference, power delivered to each resistor, and total power in the circuit. Participants are exploring concepts related to electrical resistance, power calculations, and circuit configurations.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss using the power formula P=IV and Ohm's law V=IR to derive current and voltage values. There are attempts to consolidate resistors and calculate equivalent resistance. Questions arise regarding the maximum current through specific resistors and the implications of using equivalent resistance versus individual resistor values.

Discussion Status

Several participants are actively engaging with the problem, sharing their thought processes and calculations. There is a recognition of the need to clarify the setup and assumptions, particularly regarding the maximum power and current limits for the resistors. Some guidance has been offered on approaching the calculations, but no consensus has been reached on specific values or methods.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may limit the information they can use or assumptions they can make. There is an emphasis on understanding the relationships between voltage, current, and resistance in the context of series and parallel circuits.

SmokeyMTNJim
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Here is the problem: I have already lost the ability to get the correct answer for AI

Homework Statement


28-p-007.gif

(a) What is the maximum potential difference that can be applied to the terminals a and b?
33.541
markSprite.png

Which resistor will have the largest current? V

(b) For the voltage determined in part (a), what is the power delivered to each resistor?
resistor on the left W
resistor at the top of the loop W
resistor at the bottom of the loop W

(c) What is the total power delivered to the combination of resistors?
W

Homework Equations

:
V=IR, P=IV, P=I^2R
Resistors in series = R+R+R...
Resistors in parallel (1/R)+(1/R)+(1/R)...[/B]

The Attempt at a Solution


My thought process was: If the max power to anyone resistor could be 22.5 watts then use P=IV, substitute the V for V=IR.
My equation is now P=I^2R or 22.5W = I^2 (100Ω) => I = .4743 A for current at the resistor on side A. V=IR => V=.4743(100) => V=47.43

I tried a similar method for the other side after consolidating the Resistors 1/100 + 1/100 = .2 => 1/.2 = 50. Basically a------100Ω--------50Ω--------b

No dang just thought to add these to together and get a Reqiv. for the whole thing. So i just used the same method of P=I^2R to get a I = .3873.
V=IR => 150Ω(.3873) = 58.095 V << Is this what you would get for part a? I don't really want to plug in answers yet for the problem if its wrong
 
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SmokeyMTNJim said:
Here is the problem: I have already lost the ability to get the correct answer for AI

Homework Statement


28-p-007.gif

(a) What is the maximum potential difference that can be applied to the terminals a and b?
33.541
markSprite.png

Which resistor will have the largest current? V

(b) For the voltage determined in part (a), what is the power delivered to each resistor?
resistor on the left W
resistor at the top of the loop W
resistor at the bottom of the loop W

(c) What is the total power delivered to the combination of resistors?
W

Homework Equations

:
V=IR, P=IV, P=I^2R
Resistors in series = R+R+R...
Resistors in parallel (1/R)+(1/R)+(1/R)...[/B]

The Attempt at a Solution


My thought process was: If the max power to anyone resistor could be 22.5 watts then use P=IV, substitute the V for V=IR.
My equation is now P=I^2R or 22.5W = I^2 (100Ω) => I = .4743 A for current at the resistor on side A. V=IR => V=.4743(100) => V=47.43

I tried a similar method for the other side after consolidating the Resistors 1/100 + 1/100 = .2 => 1/.2 = 50. Basically a------100Ω--------50Ω--------b

No **** just thought to add these to together and get a Reqiv. for the whole thing. So i just used the same method of P=I^2R to get a I = .3873.
V=IR => 150Ω(.3873) = 58.095 V << Is this what you would get for part a? I don't really want to plug in answers yet for the problem if its wrong
Please state the complete problem.
 
Three 100 Ω resistors are connected as shown in the figure. The maximum power that can safely be delivered to anyone resistor is 22.5W.
28-p-007.gif

(a) What is the maximum potential difference that can be applied to the terminals a and b?
33.541
markSprite.png

Which resistor will have the largest current? V

(b) For the voltage determined in part (a), what is the power delivered to each resistor?
resistor on the left
markSprite.png
W
resistor at the top of the loop W
resistor at the bottom of the loop W

(c) What is the total power delivered to the combination of resistors?
W
 
SmokeyMTNJim said:
Three 100 Ω resistors are connected as shown in the figure. The maximum power that can safely be delivered to anyone resistor is 22.5W.
28-p-007.gif

(a) What is the maximum potential difference that can be applied to the terminals a and b?
33.541
markSprite.png

Which resistor will have the largest current? V

(b) For the voltage determined in part (a), what is the power delivered to each resistor?
resistor on the left
markSprite.png
W
resistor at the top of the loop W
resistor at the bottom of the loop W

(c) What is the total power delivered to the combination of resistors?
W
SammyS said:
Please state the complete problem.

I apologize for not including that top part.
 
SmokeyMTNJim said:

The Attempt at a Solution


My thought process was: If the max power to anyone resistor could be 22.5 watts then use P=IV, substitute the V for V=IR.
My equation is now P=I^2R or 22.5W = I^2 (100Ω) => I = .4743 A for current at the resistor on side A. V=IR => V=.4743(100) => V=47.43

I tried a similar method for the other side after consolidating the Resistors 1/100 + 1/100 = .2 => 1/.2 = 50. Basically a------100Ω--------50Ω--------b

No **** just thought to add these to together and get a Reqiv. for the whole thing. So i just used the same method of P=I^2R to get a I = .3873.
V=IR => 150Ω(.3873) = 58.095 V << Is this what you would get for part a? I don't really want to plug in answers yet for the problem if its wrong
The resistor closest to point a can have a maximum current of approx. 0.4743 A.

If the equivalent resistance is 150 Ω, what voltage is required to have a current of 0.4743 A ?
 
SammyS said:
The resistor closest to point a can have a maximum current of approx. 0.4743 A.

If the equivalent resistance is 150 Ω, what voltage is required to have a current of 0.4743 A ?


Why do we use the equivalent resistance, but not the equivalent current that I found, was that an erroneous calculation?
 
SmokeyMTNJim said:
Why do we use the equivalent resistance, but not the equivalent current that I found, was that an erroneous calculation?
Look at it another way.

You can have at most 0.4743 A through the resistor on the left. Then how much current will flow through each of the two resistors that are in parallel?

Assuming you get that right, what is the voltage drop across a & b ?
 
It helps to write down the certain rules for parallel and series circuits. When Voltage (potential difference) is the same, when does it change, when does the current change, when it is the same. When I did these questions back in high school, what helped was working the problems out with easier numbers and figuring out V,I,R, at different points in circuits.
 

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