The equivalent resistance for the resistors in this circuit?

[Islam Sabry]

Homework Statement

If the circuit of parallel and series resistors , is as follows , what's the equivalent resistance for the group?

Homework Equations

neglecting the battery internal resistance... irrelevant to the question.

The Attempt at a Solution

I tried to do the following
R1=8+12=20 ohms
R2=4+6=10 ohms
R3=9 ohms
then,
R(equivalent)= R1//R2//R3

but I'm not sure!

 

[kuruman]

Ω

Homework Statement

If the circuit of parallel and series resistors , is as follows , what's the equivalent resistance for the group?

Homework Equations

neglecting the battery internal resistance... irrelevant to the question.

The Attempt at a Solution

I tried to do the following
R1=8+12=20 ohms
R2=4+6=10 ohms
R3=9 ohms
then,
R(equivalent)= R1//R2//R3

but I'm not sure!

I am not sure how the double slashes in R1//R2//R3 are interpreted mathematically. Can you imagine what the potential difference across the 9 Ω resistor might be?

 

[Islam Sabry]

means that R1 , R2, and R3 are connected in parallel ... and the question contains no voltage value..sorry if it's vague.

 

[haruspex]

R1=8+12=20 ohms

True, but not useful since the current is not flowing through these two in turn.
Create unknowns for all the voltages and currents, write down all the equations, and solve.

 

[CWatters]

For this circuit there is an easy way to solve it. Take a look at the resistor values and think about potential dividers and symmetry.

 

[NascentOxygen]

Homework Statement

If the circuit of parallel and series resistors , is as follows , what's the equivalent resistance for the group?

Homework Equations

neglecting the battery internal resistance... irrelevant to the question.

The Attempt at a Solution

I tried to do the following
R1=8+12=20 ohms
R2=4+6=10 ohms
R3=9 ohms
then,
R(equivalent)= R1//R2//R3

but I'm not sure!

Denote the nodes where the 9 Ω resistor is connected as X and Y.

Now imagine the circuit with the 9 Ω resistor temporarily removed. With the 9 Ω resistor gone, write expressions for the voltage at X and the voltage at Y.