# Simplyfing Parallel/Series Resistors in a Circuit

• Engineering

## Homework Statement

http://img463.imageshack.us/img463/997/screenshot01mu1.jpg [Broken]

## Homework Equations

V = IR
Rseries = R1 + R2 + ... + Rn
Rparallel = (1/R1 + 1/R2 + ... + 1/Rn)^-1

## The Attempt at a Solution

I simplified the circuit, to find I = 3mA. What I did was this (in order starting from far right):

6||3 = 2kohm, which is in series with 16kOhm, so 18kOhm.

The 18kOhm is in || with 9kOhm, so 6kOhm.

6kOhm is in || with 6kOhm, so total of 12kOhm.

The 12kOhm is in || with 4kOhm, as well as the 6kOhm. So I got 2kOhm for that part.

Then, then 1kOhm and the 2kOhm are in series, so that equals 3kOhm total equivalent resistence.

Then, I found that I = 3mA.

Now, it says to find I_0. I have no clue as to how to do this. I think my simplifying is correct.

Last edited by a moderator:

AlephZero
Homework Helper
Use Ohms law.

You know the current through the 1K resistor is 3 mA, so you can find the voltage across that resistor.

So, you can find the voltage across the 6K resistor. Then you can find the current through it.

Another way would be to reduce the circuit to the 1K resistor, the 6K resistor, and another resistor is parallel. You have done most of the work already, to find what the other resistor value is!

Use Ohms law.

You know the current through the 1K resistor is 3 mA, so you can find the voltage across that resistor.

V across the 1k resistor = IR = 3mA * 1kOhm = 3V

So, you can find the voltage across the 6K resistor. Then you can find the current through it.

See, this is where I'm stumped. I can just do this?:

V = IR
(9 - Vacross 1k resistor) 6V = I_0 * 6kOhm
I_0 = 1mA?

Another way would be to reduce the circuit to the 1K resistor, the 6K resistor, and another resistor is parallel. You have done most of the work already, to find what the other resistor value is!

I was thinking of doing it that way, keeping the 6kOhm and another resistor parallel to it and use the current division method. However, what should I do about the 1kOhm resistor in the way?

Last edited:
AlephZero