Resistance and DC circuit question

In summary: The equivalent resistance is used because it takes into account the total resistance of the circuit. This is important when calculating voltage, as it determines the amount of resistance the current has to overcome. The equivalent current is not used because it only takes into account the current at one point in the circuit, rather than the total current throughout the circuit.
  • #1
SmokeyMTNJim
18
0
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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  • #2
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.
 
  • #3
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
 
  • #4
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.
 
  • #5
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 ?
 
  • #6
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?
 
  • #7
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 ?
 
  • #8
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.
 

FAQ 1: What is resistance and how is it measured?

Resistance is the measure of an object's ability to resist the flow of electric current. It is measured in ohms (Ω) and can be calculated using Ohm's Law, which states that resistance is equal to voltage divided by current.

FAQ 2: What factors affect the resistance of a circuit?

The resistance of a circuit is affected by three main factors: the material of the conductor, the length of the conductor, and the cross-sectional area of the conductor. Other factors such as temperature and the presence of other components can also affect resistance.

FAQ 3: How do I calculate the total resistance of a series circuit?

In a series circuit, the total resistance is equal to the sum of the individual resistances. This can be calculated by adding together the resistance values of each component in the circuit.

FAQ 4: How do I calculate the total resistance of a parallel circuit?

In a parallel circuit, the total resistance is inversely proportional to the sum of the reciprocals of the individual resistances. This can be calculated using the formula 1/Rt = 1/R1 + 1/R2 + 1/R3 + ..., where Rt is the total resistance and R1, R2, R3, etc. are the individual resistances.

FAQ 5: How does the resistance affect the flow of current in a circuit?

According to Ohm's Law, as resistance increases, the flow of current decreases. This means that the higher the resistance in a circuit, the lower the amount of current that can flow through it. This relationship is important in understanding the behavior of circuits and designing them for specific purposes.

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