Find the two figures and the get value of the resistor and current

[Hamood97]

Homework Statement

finding the resistor and current which is following through the circuit[/B]

Homework Equations

kirchhoff law

The Attempt at a Solution

almost as fig 1 ( 9v=3.458 mA and 12v=11.122 mA)
fig 2 (9v=1.472 mA and 12v=12.882 mA) i3=2.48 mA

 

[gneill]

Hi Hamood97,

Welcome to Physics Forums!

View attachment 113220

Homework Statement

finding the resistor and current which is following through the circuit[/B]

I presume that you are required to find the resistance R3? (It's hard to tell because the writing on the image is very small). What current are you meant to find?

Homework Equations

kirchhoff law

The Attempt at a Solution

almost as fig 1 ( 9v=3.458 mA and 12v=11.122 mA)
fig 2 (9v=1.472 mA and 12v=12.882 mA) i3=2.48 mA

Is that meant to specify the currents produced by the voltage sources? It doesn't make sense to equate voltages and currents in an equation so that is my guess. The diagram doesn't indicate where i3 is.

 

[Hamood97]

thanks for your reply. i should have told you before about value of R3 which is 560 ohm. i want to find all the currents in figure 1 and figure 2.

 

[gneill]

Okay, perhaps to avoid confusion you should annotate your drawing to show currents and their directions.

What circuit analysis technique(s) have you applied? Can you show your work?

 

[Hamood97]

R3 =560

 

[gneill]

It really would be better if you could type in your equations. It's hard to make out others' handwriting when it's sideways.

You didn't identify your loop currents on the diagram, but after looking at your equations I determined that this was where you started and that you chose to use mesh current analysis:

It would better if you stated these things so that others don't have to puzzle it out before thy can help you. Typing in your equations would also be a big help. That way helpers can easily quote them for commentary.

Your mathematical results for the three mesh currents look okay to me.

Your experimental results for figure 2 look a bit off if the math is to be believed. Perhaps not all the resistor values are precise (cheap resistors can be +/- 20% in value)? Did you measure the voltage source values while the circuit was in operation (to make sure they didn't change value under load)?