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

#### Daniel2244

1. 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.

2. Homework Equations
R=V/I, 1/Rt=1/R1+1/R2

3. The Attempt at a Solution 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) 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.

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#### magoo

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?

#### BvU

Homework Helper
1. 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.

#### Daniel2244

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

#### Daniel2244

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.