# Homework Help: Solve the Circuit For Electromagnetism Unit

1. Jan 19, 2010

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

please visit this site and solve with calculations, Thank you!

http://rapidshare.com/files/338079894/Figure_it_out.doc

2. Relevant equations

V=IR

Rt=1/R1+1/R2+1/R3

3. The attempt at a solution

Thank You

Last edited by a moderator: Apr 24, 2017
2. Jan 20, 2010

### Yitzach

You are missing a relevant equation and you have no idea what one of the others is good for.
$$R_t=R_1+R_2+R_3...$$ for resistors in series.
$$\frac{1}{R_t}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R_3}...$$ for resistors in parallel.
You have a series-parallel circuit so both apply in certain parts.

3. Jan 20, 2010

Its just i am working on it but i need the anwers so i can check if i get it right. Please i have a test tomorrow

4. Jan 20, 2010

### Yitzach

Then show your answers and we might be able to help more.

5. Jan 20, 2010

ok so i have the answers can you please check to see if i'm right:

I1=4.0A
R1=3.8 ohms
R4=5.0 ohms
I2=2.0 A
I3=2.0 A
V2=20.0V
V3=20.v
I0=4.0A
Rt=10 ohms
V4=?
Rt=10 ohms

6. Jan 20, 2010

### Yitzach

You can check the V=IR across all components and their combinations to see if they make sense. If not your answers are not correct. I agree with $$I_0, I_1, I_2, I_3, V_2, V_3,\ and\ R_1$$ for now. I have something else to do. I'll check the rest later.

7. Jan 20, 2010

great, thank you!

8. Jan 20, 2010

is v4=15v
R4=3.8

9. Jan 21, 2010

### Yitzach

I agree with all answers except R4 and V4. Don't assume symmetry because both have 4A going through them. That current must go through the whole circuit, ie both R1 and R4.
Look at your configuration of resistors and find the equation that fits. You have two parallel resistors in series with two other resistors. And solve for R4. Then apply V=IR to that resistor.
For resistors in parallel, I solve for RT before entering it into my calculator or into a series equation like you will:
$$R_T=(\frac{1}{R_1}+\frac{1}{R_2}+...)^{-1}$$

10. Jan 21, 2010

would r4 = 1.25 and v4 = 5

because if i make the parallel part of the series by doing Rt=1/ri + 1/r2...
than it will be 5 ohms and is series, the equation is rt=r1+r3+r4
10=3.75+5+r4
r4= 1.25

11. Jan 21, 2010

### Yitzach

There you have it. Good luck with the exam.