# Kirchhoff's Law

1. Mar 23, 2004

### TJ

Kirchhoff's Law problem. I have figured most of the problems but these two has me stumped. Please help.

Please see the figures and my questions at http://quasarsvc.bizland.com/DC_Circuit.doc [Broken]

http://quasarsvc.bizland.com/DC_Circuit.doc [Broken]

Last edited by a moderator: May 1, 2017
2. Mar 23, 2004

### Chen

Find the equivalent resistance of $$R_5$$, $$R_6$$ and $$R_7$$, which are connected in parallel, and call it $$R_{5,6,7}$$. Find the equivalent resistance of $$R_4$$ and $$R_{5,6,7}$$, which are connected in series, and call it $$R_{4,5,6,7}$$. Find the equivalent resistance of $$R_3$$ and $$R_{4,5,6,7}$$, which are connected in parallel, and call it $$R_{3,4,5,6,7}$$. Find the equivalent resistance of $$R_1$$ and $$R_2$$, which are connected in parallel, and call it $$R_{1,2}$$. Finally find the equivalent resistance of $$R_{1,2}$$, $$R_{3,4,5,6,7}$$ and $$R_8$$, which are connected in series, and that is the equivalent resistance of the whole circuit.

3. Mar 23, 2004

### Chen

The numbers in the loop problem represent the potential drop on each of the resistors. To find the value of the potential drops you have to find the current through each of the resistors, and to find that you first need to find the equvilanet reisstance of the whole circuit.

4. Mar 23, 2004

### TJ

RE: post236, m1374

1) R567 = 10
2) R567+R4 = 20
3) R4567+R3 = 12
4) R1&R2 = 12
5) R12(12)+R34567(12)+R8(6) = 30 = Rt ?
TJ

5. Mar 23, 2004

### Chen

Yes it's $$30\Omega$$ in the first question.

6. Mar 23, 2004

### TJ

Post 237

Thank you for acknowledging the Rt so I can work the rest of them

7. Mar 23, 2004

### TJ

237

Have E1,E2,E3 = 12v
Have I1=0.6, I2=0.4, I3=0.4
Have P1=7.2, P2=4.8,P3=4.8
need understanding of "how to" relating to R4=10, Et=30, Rt=30 It=1.0 to complete E4 or I, and would not that E value be the same for E5, E6, E7, E8?
Thanks
TJ