Current and Potential difference in a circuit


by Xaspire88
Tags: circuit, current, difference, potential
Xaspire88
Xaspire88 is offline
#1
Oct10-07, 10:01 PM
P: 100
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 cant figure out what to substitute in to 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 im stuck
Attached Thumbnails
circuit.JPG  
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pooface
pooface is offline
#2
Oct10-07, 11:56 PM
P: 210
I can't see the attachment. maybe you should upload to imageshack or something.
Xaspire88
Xaspire88 is offline
#3
Oct10-07, 11:59 PM
P: 100
http://img77.imageshack.us/content.p...circuitus9.jpg

there is the link to the img file

pooface
pooface is offline
#4
Oct11-07, 12:08 AM
P: 210

Current and Potential difference in a circuit


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
Xaspire88 is offline
#5
Oct11-07, 12:22 AM
P: 100
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
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#6
Oct11-07, 12:32 AM
P: 210
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
Xaspire88 is offline
#7
Oct11-07, 12:34 AM
P: 100
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
pooface is offline
#8
Oct11-07, 12:43 AM
P: 210
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
Xaspire88 is offline
#9
Oct11-07, 12:49 AM
P: 100
im afraid i dont see

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

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

4+8=12?

where did i go wrong?
pooface
pooface is offline
#10
Oct11-07, 12:53 AM
P: 210
sorry. I assumed you didn't include R1 in Req. Nevermind what I said you are on the right track.
Xaspire88
Xaspire88 is offline
#11
Oct11-07, 01:09 AM
P: 100
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
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#12
Oct11-07, 01:19 AM
P: 210
I havent 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
Xaspire88 is offline
#13
Oct11-07, 01:24 AM
P: 100
yeah i think its right tried circuit maker earlier and got confused :) thanks for the help
LemonLe
LemonLe is offline
#14
Oct15-07, 05:14 AM
P: 1
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 im still not sure but i hope these answer will help.


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