Physics homework?

Question

Can anyone explain how to solve for the total effective resistance of the combination of resistors shown in this link.

http://tinypic.com/view.php?pic=bf2xpk&s=2

Answer 1

Sure

The rules are:
Parallel combine as
1/Req=1/R1+1/R2+...+1/RN


for two resistors in parallel
Req=(R1*R2)/(R1+R2)

Series resistors add
Req=R1+R2+...+RN

for this circuit, start with the parallel 12 and 5 ohm resistors
Req=(12*5)/(12+5)
=60/17

Add to the 10 ohm
Req=10+60/17
=230/17

This is in parallel with the 7 ohm
Req=(230*7/17)/(230/17+7)
=4.6 ohm

j