# Homework Help: R and I of DC circuit

1. Apr 29, 2014

### scrubber

1. The problem statement, all variables and given/known data
http://postimg.org/image/8oweasluj/
Each rectangle in the figures represents a resistor with resistance=2.9kΩ.

a) What is the net resistance of the circuit of Fig 1 connected to the battery? Each resistance has R=2.9 kΩ.

b) What is the current flowing into the junction c and the branch of ca from the battery?

c) If we replace the branch of bc with a 12V battery as Fig 2 shows and Vb>Vc, what is the current flowing into the branch of CA?

3. The attempt at a solution

a) Is the circuit in Fig 1 equal to that of Fig 3 as below?
http://postimg.org/image/t5cwrllzt/

Thank you.

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2. Apr 29, 2014

### Sumanth

Yes, you can take it and solve it

3. Apr 29, 2014

### scrubber

Thank you so much!! :D
I know part a then, just apply the parallel and series equations.

But for part b, does it mean that first I have to calculate the total current =It,
then apply Ic=It*(Rt-Rc/Rt), where Rt represents the total resistance?

4. Apr 29, 2014

### Sumanth

No, just apply ohm's law

5. Apr 29, 2014

### Sumanth

V=ir. R means effective resistance
"i"means total current through the cell.
And then divide current into the branches of circuit in corresponding ratios.

6. Apr 29, 2014

### scrubber

I see! I understand now :D Thank you so much!!
Should I use Kirchhoff's Rule? But can Kirchhoff's Rule be applied if there's more than two loops?

7. Apr 29, 2014

### scrubber

And in part b, the current flowing into junction c and branch ca would be the same then?
(Since the ratio of resistance are the same?)

8. Apr 29, 2014

### scrubber

For part b, can I rather use V=IR to find out the current through branches directly after finding out the total current?

9. Apr 29, 2014

### Sumanth

Kirchoff law can be applied separately to any number of loops and solve then separately to find currents