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Need Help With SeriesParallel Ohms Law Circuit Math Problem 
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#1
Dec2311, 07:57 PM

P: 14

1. The problem statement, all variables and given/known data
Total Volts: 10 Resistor 1  R1: 1K Resistor 2  R2: 4K Resistor 3  R3: 4K Photo That I Made Of The SeriesParallel Circuit: http://imageshack.us/photo/myimages/266/circuitn.png/ 2. Relevant equations http://en.wikipedia.org/wiki/Series_...allel_circuits 3. The attempt at a solution Total Current: 0.5 Voltage Across R1: 0.167 Current Through R3 In Amps: 0.5 Current Through R2: 0.333 Total Circuit Power In Watts: 3 Power Consumed By R3 In Watts: 1.5 


#2
Dec2311, 08:57 PM

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How'd you come up with those answers?



#3
Dec2311, 09:02 PM

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((NOTE: Where the question "What Is the Current Through R1 In Amps?", it should read "R2" instead.)) Known Circuit Values: Total Voltage: 10 Volts Resistor 1  R1  In Series  Value: 1K Resistor 2  R2  In Parallel With R3  Value: 4K Resistor 3  R3  In Parallel With R2  Value: 4K Questions: 1. What Is The Total Current Equal to In Amps? 2. What Is The Voltage Across R1? 3. What Is The Current Through R3 In Amps? 4. What Is The Current Through R2 In Amps? (I First Listed It As R1 In The Pic, But It Should Be R2). 5. What Is The Current Value Through R1 In Watts? 6. What Is The Total Power Consumed In Watts? 7. What Is The Power Consumed By R3 In Watts Can anyone help me out here? 


#4
Dec2311, 09:33 PM

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Need Help With SeriesParallel Ohms Law Circuit Math Problem
How are you going about determining this:
1. What Is The Total Current Equal to In Amps? 


#5
Dec2311, 09:42 PM

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We want to see your actual calculations so we can see where you are going wrong.



#6
Dec2311, 09:55 PM

P: 14

Are you referring to question 5 "5. What Is The Current Value Through R1 In Watts?"? That should be Amps. My mistake. And I will see if I can post some of my notes here, to help you figure out what I am doing wrong. I have a bunch of them, but I don't know if I can write them in a way to actually explain what steps that I have been taking so far. 


#7
Dec2311, 10:27 PM

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Start at the beginning. I'd like to see how you determine the current flowing from the 10v source.



#8
Dec2311, 10:38 PM

P: 14

For the 10 Volts and Current, I created a chart based on what I found on a site dealing with this type of math. I can't create the chart in the thread, but I can try and list some of the math problems that I used. Since all Voltage is equal in a parallel circuit, the top of the chart had 10 Volts listed as all of the answers. The Amps came out to, R110, R22.5, R32.5, for a total of 15. The Resistance on the chart had the Resistance as R11, R24, R34, for a total of 0.666. I know the chart came out to be wrong, because the answers didnt match any of the choices. Can you tell me what I did wrong? This chart worked on all of my Series math problems, but the version for Parallel didn't match up. 


#9
Dec2311, 10:44 PM

P: 14

There is one other problem that I have been having problems with. Its a True or False question. Can anyone here help me find the answer?
If all Resistors in a Parallel circuit are equal size, then the Current through each is Equal? True or False? 


#10
Dec2311, 10:53 PM

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resistors in your circuit. 


#11
Dec2311, 10:56 PM

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Do you know Ohm's Law? Can you answer questions such as: if a 100 ohm resistor has 0.5 amps flowing through it, what reading would a voltmeter give if you connected it across the two terminals of that resistor?



#12
Dec2311, 10:57 PM

P: 14

How would I use this to help me solve the two 4K resistors? And the "K" means 1000 right? So its actually 4000 or .1000? 


#13
Dec2311, 11:04 PM

P: 14

Yeah I know Ohms Law, but I am having a problem figuring out SeriesParallel math. I x V = 50 Volts. At least I think that is right. 


#14
Dec2311, 11:09 PM

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#15
Dec2311, 11:27 PM

P: 14

So have I posted enough to where you can start helping me figure out this math? Like tell me which formulas to use for each question? 


#16
Dec2311, 11:54 PM

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The "formula" for any number of resistors in parallel is easiest remembered as:
1/R = 1/R_{1} + 1/R_{2} + 1/R_{3} + ... So work out the sum of the reciprocals, then take the reciprocal of that. For 2 resistors in parallel, this boils down to: R = (product of the resistances) / (sum of the resistances) Does that help? 


#17
Dec2411, 12:11 AM

P: 14

How do I find the Total Current? The Voltage Drop over R1? The current through R1, R2 and R3? Find Total Watts? The Watts consumed by R3? 


#18
Dec2411, 12:18 AM

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Once you have worked out the resistance of the 2 in parallel, you can then treat that pair as a single resistance. It is in series with R1, so you add your answer to the resistance of R1 to arrive at the total circuit resistance. For resistances in series, their values simply add together.



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