Current and Potential difference in a circuit

[Xaspire88]

For the circuit shown find the current through and the potential difference across each resistor.

i was using the loop rules to make equations i could substitute into each other to solve this.. but i got stuck when i was making the last one for the currents...

thus far i have
I3= I4+I5
I1= I2+I3
and thus I1= I2+I4+I5
which then is 0=-I1+I2+I4+I5
but i need to find one with all of the currents but i can't figure out what to substitute into get an equations with I3 in it as well. Help please

loop 1 0= -I1R1 -I3R3 - I5R5 +24
loop 2 0= -I1R1 -I2R2 +24
loop 3 0= -I2R2 +I3R3 +I4R4 +24
loop 4 0= -I4R4 +I5R5
and then i need 0= the equation for the currents..
that way i can plug it into a simultaneous solver.. but I am stuck

 

[pooface]

I can't see the attachment. maybe you should upload to imageshack or something.

 

[Xaspire88]

http://img77.imageshack.us/content.php?page=done&l=img77/4002/circuitus9.jpg

there is the link to the img file

 

[pooface]

Ok, all this loop stuff is not necessary and according to me it adds confusion.

Use your series-parallel formulae to reduce the circuit and systematically find the voltage drops and currents.

circuits are usually reduced from the right to left when a single source is on the left.

See what you can do.

 

[Xaspire88]

well i tried that at first. i determined the equivalent resistance of the circuit to figure out the current the first resistor would receive. i determined this to be 2 amps. the Req= 12 ohms.. but then i just seemed to get confused.. the current going into the first resistor equals that of the total current going into the rest of the resistors.. hmm

 

[pooface]

Ok so 2 amps through R1 so VR1 = 8V correct?

24V-8V=16V which is the voltage across the rest of the circuit.

hmmm can you see what to do from there?

 

[Xaspire88]

I think i have an idea :) 16V for the rest of the circuit, but doesn't the rest of the circuit also receive a total of 2amps? oh i see when it splits they both receive the same Voltage because they are in parallel. so the 24ohm resistor receives 16volts as does the Req of the other line.

 

[pooface]

Req should be 8 ohms not 12 ohms. go back and do it again and see where you went wrong.

and yes current from the 16 volts gives the rest of the circuit a total of 2 amps.

 

[Xaspire88]

im afraid i don't see

1/(1/8+1/24)+6= 12

1/(1/12+1/24)= 8

4+8=12?

where did i go wrong?

 

[pooface]

sorry. I assumed you didn't include R1 in Req. Nevermind what I said you are on the right track.

 

[Xaspire88]

so from there i would gather that ... 16 volts goes to the 24ohm resistor 16V=Ix24 I=2/3A
16 volts goes to the other wire with a Req of 12 ohms. 16V= I 12ohms I= 1 1/3 amps..

1 1/3 amps is the current that would go to each the 6 ohm resistor and the 6Req of the others. V= 1 1/3 amps x 6ohms V=8 volts ... 8 volts goes to each the 24 ohm resistor and the 8 ohm resistor since they are in parallel (had series typed). 8v= I24ohms I= 1/3 amps, and lastly 8V= I 8ohms I= 1 amp.. confusing possibly. but what do you think?

 

[pooface]

I haven't worked the values out myself but I do not see anything wrong with your method. everything looks good. amazing!
A good way to confirm your values is to use simulation software like circuit maker. Search for it. I think it is freeware since the company that made it went bankrupt.

Simulation software will become very important as you progress through your course.

 

[Xaspire88]

yeah i think its right tried circuit maker earlier and got confused :) thanks for the help

 

[LemonLe]

This is what i got:
R1= 4 ohms, I1= 2A, V1= 8V drop
R2= 24 ohms, I2= 2/3A, V2= 16V drop,
R3= 6 ohms, I3= 4/3A, V3= 16V drop
R4= 8 ohms, I4= 1/3A , V4= 16V drop
R5= 24 ohms, I5= 1A , V5= 16V drop

They should be right but I am still not sure but i hope these answer will help.