# Homework Help: Res-monster Maze

1. Jul 29, 2014

### Zondrina

1. The problem statement, all variables and given/known data

Res-monster maze. In the following figure, all the resistors have a resistance of $4.0 \Omega$ and all the (ideal) batteries have an emf of $4.0 V$. What is the current through resistor $R$?

2. Relevant equations

$\sum V = 0$
$\sum I = 0$
$V = \epsilon$
$V = IR$

3. The attempt at a solution

See the attached image.

When I look at it, I see two loops. The big loop to the left of $R$ and the smaller loop to the right of it. Would I just apply the equations in that sense?

Left loop:

$\epsilon_1 - i_1R - i_2R' - i_3R'' = 0$

Right loop:

$\epsilon_2 - i_4R''' + i_5R = 0$

EDIT: Wait what if I just find an equivalent resistance for that one standout parallel resistor combination?

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Last edited: Jul 29, 2014
2. Jul 29, 2014

### Staff: Mentor

The easy way is to see whether there exists a string of nothing but pure voltage sources between one end of R and its other end. Any other method will be many orders of magnitude more complicated.

You know how to play snakes-and-ladders, right?

3. Jul 29, 2014

### Zondrina

I attached a picture of what I think you mean.

Writing the loop equation now:

$iR + \epsilon_1 - \epsilon_2 - \epsilon_3 - \epsilon_4 = 0$
$i = \frac{- \epsilon_1 + \epsilon_2 + \epsilon_3 + \epsilon_4}{R}$
$i = \frac{8.0 V}{4.0 \Omega}$
$i = 2 A$

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• ###### Screen Shot 2014-07-30 at 12.30.28 AM.jpg
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4. Jul 30, 2014

### Staff: Mentor

That looks right.