# Homework Help: Design a Circuit

1. Jul 29, 2014

### Zondrina

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

You are given two ideal batteries with $\epsilon_1 = 1.5 V$ and $\epsilon_2 = 9.0 V$. You are also given three $120 \Omega$ resistors.You may use any or all of the components. Design a circuit where there is a current of $21 \pm 1 mA$ through at least one of the resistors.

Do NOT use EMF sources in parallel.

2. Relevant equations

3. The attempt at a solution

I've already tried several combinations of resistors and batteries with no avail. The closest I've been is when all three resistors are in series with the $9.0 V$ emf. Then the current across the whole circuit is $25 mA$. I've also tried creating several multiloop circuits, but those haven't worked either.

Anyone have some design advice? It would be very appreciated.

EDIT: Never mind guys I got it, just place the resistors in series and then oppose the emfs. Then the current is $\frac{9.0-1.5}{360} = 21 mA$.

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

### phinds

glad to see you got it. I've never understood the utility of such problems, they just seem silly to me but I've seen them before.