Finding the currents in this system

• Dell
In summary: A which lies between R3 and ε2, and point B which is between R1 and ε1,you need the potential difference across E2 and across R1 (or across E1 and across R3):smile:sorry meant to be v=ε2-I1R1=2-0.2=1.8,but is it okay to just ignore the whole part that includes R2 and I2??sorry meant to be v=ε2-I1R1=2-0.2=1.8,
Dell
given the following:
http://lh6.ggpht.com/_H4Iz7SmBrbk/Sg04JIIg9vI/AAAAAAAAA-o/xDycbG90Gmc/s720/C.jpg

and given that

ε1=3V
ε2=2V
R1=1Ω
R2=2Ω
R3=3Ω

i am asked to find the current flowing throiught R1,R2, R3

what i did was

I3=I2+I1
I1R1-I2R21

but i am short of one equation to solve this, what i would like to do is somehow find R12, as an the sum of R1 and R2, but my problem is that i have ε1 between them and i have no idea how to tackle this,

had ε1 noot been there i would have said R12=(1/R1+1/R2)-1 and then i could make a third equation using this.

how can i solve this?

Last edited by a moderator:
Dell said:
I3=I2+I1
I1R1-I2R21

but i am short of one equation to solve this, what i would like to do is somehow find R12, as an the sum of R1 and R2, but my problem is that i have ε1 between them and i have no idea how to tackle this,

Hi Dell!

Stop trying to simplify it … it's simple enough already!

There are three loops, of which two are independent …

you've already applied Kirchhoff to the R1R2-loop, so now just apply it to the R2R3-loop.

thanks,.. for the second part of the question they ask what the difference in voltage is from pioint A which lies between R3 and ε2, and point B which is between R1 and ε1,

can i use kirchhoff here too, and igonre the part with R2 and R3, so I1R1=ε1-v
v=ε1-I1R1=2.8

?

Dell said:
thanks,.. for the second part of the question they ask what the difference in voltage is from pioint A which lies between R3 and ε2, and point B which is between R1 and ε1,

can i use kirchhoff here too, and igonre the part with R2 and R3, so I1R1=ε1-v
v=ε1-I1R1=2.8

?

sorry, I don't understand that … and what happened to E2?

You need the potential difference across E2 and across R1 (or across E1 and across R3)

sorry meant to be v=ε2-I1R1=2-0.2=1.8,

but is it okay to just ignore the whole part that includes R2 and I2??

Dell said:
sorry meant to be v=ε2-I1R1=2-0.2=1.8,

but is it okay to just ignore the whole part that includes R2 and I2??

Yup … Kirchhoff applies to only one loop at a time!

What is the purpose of finding the currents in a system?

The purpose of finding the currents in a system is to understand and analyze the flow of electrical energy or charge through the system. This information is crucial for designing and optimizing electrical circuits and systems.

What are the different methods for finding currents in a system?

The two main methods for finding currents in a system are Kirchhoff's current law (KCL) and Ohm's law. KCL is used for analyzing complex circuits with multiple branches, while Ohm's law is used for simpler circuits with only one branch.

How do I apply Kirchhoff's current law to find currents in a system?

Kirchhoff's current law states that the sum of all currents entering and exiting a node (junction point) in a circuit must be equal to zero. To apply this law, you would need to label the currents in each branch and set up equations based on the currents entering and exiting each node.

What are the key factors that affect the current in a system?

The key factors that affect the current in a system are the voltage, resistance, and the type of conductor used. Higher voltage and lower resistance will result in a higher current, while a non-conductive material will not allow any current to flow through the system.

How can I use the current values to troubleshoot issues in a system?

By knowing the expected current values in a system, you can compare them to the actual measured values to identify any discrepancies. This can help in troubleshooting issues such as faulty components, loose connections, or incorrect wiring.

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