How to calculate resistance in a combined circuit using V&I

In summary, the student is trying to solve a problem using equations and trying to calculate the resistance of a circuit. They have the results of an experiment and need to calculate the resistance of the circuit using the current.
  • #1
Daniel2244
125
5

Homework Statement


I am not sure how to calculate the resistance of the circuit and each resistor using voltage and current. I know how to work the resistance out in series and parallel but am 100% how to work it out in combined.

Homework Equations


R=V/I, 1/Rt=1/R1+1/R2

The Attempt at a Solution


upload_2018-3-5_21-13-30.png

A1=5MA, A3=2.5MA, A5=1.7, and voltage is 1V
So, would I do 1/0.0025=400Ω (not correct max R should be 300Ω)? Maybe I should have added another ammeter between R1 and R2 or after R2 on the same branch?. Now, because I have the resistance worked out for the resistors in series would I work out the resistance for R3? R3=1/0.0017=588.24 (also very wrong)

upload_2018-3-5_21-27-42.png

Finally, by adding R1 and R2 turning it into one resistor (400Ω) could I turn the circuit into a parallel circuit to work out total resistance? 1/Rt=1/400+1/588.24.24=4.1999864e-3 Rt=1/4.1999864e-3=238.1Ω.
 

Attachments

  • upload_2018-3-5_21-13-13.png
    upload_2018-3-5_21-13-13.png
    33.4 KB · Views: 530
  • upload_2018-3-5_21-13-30.png
    upload_2018-3-5_21-13-30.png
    1.9 KB · Views: 456
  • upload_2018-3-5_21-27-21.png
    upload_2018-3-5_21-27-21.png
    2.3 KB · Views: 501
  • upload_2018-3-5_21-27-42.png
    upload_2018-3-5_21-27-42.png
    2.3 KB · Views: 441
Physics news on Phys.org
  • #2
I couldn't read the attachment 1. If the first drawing in your attempt to solve is correct, you have R1 in series with R2. What is the total resistance in that branch?

Note that R3 is in parallel with the R1 + R2.

What is the value of R3 compared to R1 + R2?

In your attempt, what does the quantity 1/0.0017 represent?
 
  • #3
Daniel2244 said:

Homework Statement


I am not sure how to calculate the resistance of the circuit and each resistor using voltage and current. I know how to work the resistance out in series and parallel but am 100% how to work it out in combined
This is NOT a problem statement. You don't tell us what is given and what is asked of you.

Sorry, but your attachments are illegible.
 
  • #4
magoo said:
I couldn't read the attachment 1. If the first drawing in your attempt to solve is correct, you have R1 in series with R2. What is the total resistance in that branch?
https://gyazo.com/234be2533d0fe8a92cf622435f61d413 - this is the first attachment.

[/QUOTE]Note that R3 is in parallel with the R1 + R2.[/QUOTE] Yes, that's why I worked out the total resistance for R1 + R2 because they were is series. Then I worked out the resistance of R3 using R=V/I, the using the equation 1/Rt=1/R1+1/R3 (bearing in mind R1 is this equation is R1 and R2 added together) I worked out the total reistance

[/QUOTE]What is the value of R3 compared to R1 + R2?[/QUOTE]
R3=588.24 Ω R1+R2=400Ω
[/QUOTE]In your attempt, what does the quantity 1/0.0017 represent?[/QUOTE]
Resistance of R3. I changed 1.7mA to 0.0017A
 
  • #5
BvU said:
This is NOT a problem statement. You don't tell us what is given and what is asked of you.
The results I got from the experiment carried out: A1=5MA, A3=2.5MA, A5=1.7, and voltage is 1V
Using these results I have to calculate the resistance of the total resistance of the circuit at 1v using the current.

Sorry, but your attachments are illegible.
Attachment 1: https://gyazo.com/234be2533d0fe8a92cf622435f61d413
Attachment 2:https://gyazo.com/d191a48c47c6c0f87df0163f7b89ae64
Ignore the numbers next to the ammeters they're not relevant.
 

1. How do I calculate the total resistance in a combined circuit?

To calculate the total resistance in a combined circuit, you must first determine the individual resistances of each component in the circuit. Then, you can use the formula R(total) = R1 + R2 + R3 + ... to find the sum of all resistances. This will give you the total resistance of the combined circuit.

2. What is the formula for calculating resistance in a combined circuit?

The formula for calculating resistance in a combined circuit is R(total) = R1 + R2 + R3 + ..., where R(total) is the total resistance and R1, R2, R3, etc. are the individual resistances of each component in the circuit.

3. Can I use Ohm's Law to calculate resistance in a combined circuit?

Yes, you can use Ohm's Law (V = IR) to calculate resistance in a combined circuit. Simply rearrange the formula to solve for resistance (R) and plug in the values for voltage (V) and current (I) in the circuit.

4. What units are used to measure resistance?

The unit used to measure resistance is the ohm (Ω). This unit is named after the German physicist Georg Ohm and is represented by the Greek letter omega (Ω). Other common units for measuring resistance include kilohms (kΩ) and megohms (MΩ).

5. How does the number of resistors in a combined circuit affect the total resistance?

The more resistors there are in a combined circuit, the higher the total resistance will be. This is because each resistor adds its own resistance to the circuit. However, if the resistors are connected in parallel, the total resistance will be lower than if they were connected in series.

Similar threads

  • Introductory Physics Homework Help
Replies
4
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
1K
  • Introductory Physics Homework Help
Replies
3
Views
526
  • Introductory Physics Homework Help
Replies
11
Views
1K
  • Introductory Physics Homework Help
Replies
19
Views
6K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
2
Replies
60
Views
7K
  • Introductory Physics Homework Help
Replies
13
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
Back
Top