Circuit 1

[tinhnho]

hi everyone

i have a trouble to do this proplem, even i already read the comment hints ,can anyone please help me with this proplem, Thanks for reading

here is the question : http://www.viethost4u.com/toan/circuit.GIF

p/s: is the answer 1.2A ?

[enigma]

Can you please post what you've tried, tinhnho?

[tinhnho]

the problem is to analyze all equipotential points and join them... also if a resistor is connected between 2 equipotential points then that resistor can disconnected from the circuit for analysis..(because no current flows thru equipotent points)

the current from the battery, due to symmetry of the circuit divides itself equally into three parts to enter branch 1,2,3
from the symmetry of the circuit connection we see that points 1,2,3 will have same potential and hence can be connected together.
similarly points 4,5,6 also have same potential (but not equal to that of 1,2,3)
therefore at this intermediate stage the equivalent circuit consists of 2 sets of 3 resistors connected in parallel..
now all that left to do is to connect the remaining(6 resistors) resistors between these to points in parallel
thus we have 2 sets of 3 resistors in parallel and 1 set of 6 resistors in parallel...
the net resistance taking all resistors to be 1 ohm is 12
source voltage is 1 V...therefore current is 1.2A


The simplified circuit looks like this…forgive me for the crude drawing…that’s the best I could make. http://www.viethost4u.com/toan/pic_c.GIF

[ehild]

the problem is to analyze all equipotential points and join them... also if a resistor is connected between 2 equipotential points then that resistor can disconnected from the circuit for analysis..(because no current flows thru equipotent points)

the current from the battery, due to symmetry of the circuit divides itself equally into three parts to enter branch 1,2,3
from the symmetry of the circuit connection we see that points 1,2,3 will have same potential and hence can be connected together.
similarly points 4,5,6 also have same potential (but not equal to that of 1,2,3)
therefore at this intermediate stage the equivalent circuit consists of 2 sets of 3 resistors connected in parallel..
now all that left to do is to connect the remaining(6 resistors) resistors between these to points in parallel
thus we have 2 sets of 3 resistors in parallel and 1 set of 6 resistors in parallel...
the net resistance taking all resistors to be 1 ohm is 12
source voltage is 1 V...therefore current is 1.2A


The simplified circuit looks like this…forgive me for the crude drawing…that’s the best I could make. http://www.viethost4u.com/toan/pic_c.GIF

It is correct. Good job, tinhnho!

[tinhnho]

i think the current should be -1.2A for final answer right ?

[ehild]

i think the current should be -1.2A for final answer right ?
According to my logic, the answer for the question "how much current" is
1.2 A. For the question about the sign, the answer is "-". But my logic might be different from your teacher's.

ehild

[spacecowboy]

I think the answer is 1.2A~, but this valure should be negetive, according to the direction of the current. It's just my point.. :redface: