# A Question about Series-Parallel Circuits

1. Oct 21, 2013

### bibo_dvd

Hello Guys !!

In This photos i found that
in (a) : RT= 4 Ω+ 10 Ω+ 4 Ω= 18 Ω
and
in (d) : RT= 10 Ω

but i can't understand why in (a) the total resistance equals to 18 and how will the current would pass ??

and in (d) i can't understand why the total resistance equals to 10 and why we didn't take the two 4 ohm resistances in the count ?!!

Thank you Guys !!

2. Oct 21, 2013

### Jony130

Current can flow only in close loops so for example A

In circuit D you have a short wire. And all current will flow through shorted wire.

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3. Oct 21, 2013

### zamalek fc

why not R=4+4=8Ω ??

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4. Oct 21, 2013

### Integral

Staff Emeritus
What is in parallel with those 2 resistors? What is the resistance of a wire? How do you find the resistance of a parallel network?.