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Voltage drop and current for each resistor

by alan1592
Tags: current, resistor, voltage
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alan1592
#1
May8-10, 09:31 PM
P: 8
1. The problem statement, all variables and given/known data
heres a picture of the problem. Please dont give me the answer just tell me what are the steps to complete it. thanks.

http://i307.photobucket.com/albums/n...download-1.jpg
2. Relevant equations

V=IR

3. The attempt at a solution

1/6+1/3=2 Ohms
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Fronzbot
#2
May8-10, 10:34 PM
P: 62
Ok, so you now have two resistors in the circuit- you can calculate the voltage drop across each resistor and, using Ohm's law, the current. You need to be a little more specific with what you're looking for so you can get more help.
alan1592
#3
May8-10, 11:09 PM
P: 8
Im looking to find those items. The voltage drop and the current. I dont know how.

fallen186
#4
May8-10, 11:52 PM
P: 41
Voltage drop and current for each resistor

Since there is one indepedent voltage source of 20 Volts that means the voltage drop across all the resistors should equal 20V.

I would have made this look nice but the LaTex Isn't working.

First Combine the Resistors in Parrallel:
1/R =(1/R_1)+(1/R_2)+...(1/R_N)
1/R = (1/6 Ohm) +(1/3 Ohm)
1/R = (1/6 Ohm) + (2/6 Ohm)
1/R = (3/6 Ohm) = (1/2 Ohm)

1/(1/2 Ohm) = R = 2 Ohm

So now you have
---||----^^^^---^^^^-|
|___________________|

Sorry for the bad drawing
( --||-- = voltage source, ^^^^ = resistor)


Now combine the resistors in series
R= R_1 +R_2+...R_N
R= 3 Ohm + 2 Ohm
R = 5 Ohm

So now you have

---||---^^^^--|
|____________|

Using V = IR you can solve for the current:
V=IR
(20 Volts) = I * (5 Ohm)
I = 4 Amperes

Now split the circuit back up so that it is 2 resistor in series.
Resistors in series have the same current
---||----^^^^---^^^^-|
|___________________|

So for the first resistor (3 Ohm resistor)
V = IR
I = 4 Ampere
R = 3 Ohms

V = (4 Ampere)(3 Ohm)
V= 12 Volts
Voltage on the 3 Ohm resistor directly right of the independent voltage source is 12 volts


Now for the second resistor (2 Ohm Resistor)
V = IR
I = 4 Ampere
R = 2 Ohms

V = (4 Ampere)(2 Ohms)
V = 8 Volts
Voltage on the 2 Ohm resistor directly right of the 3 Ohm resistor is 8 volts.

Split it up so you are back with the circuit you were first with.
---||---^^^^-.----^^^^--|
|___________|----^^^^--|

Resistors in parrallel have the same voltage so:
6 Ohm Resistor in Parrallel:

V=IR
(8 volts) = I * (6 Ohm)
I = (4/3) Amperes

3 Ohm Resistor In parrallel:

V= IR
(8 Volts) = I * ( 3 Ohm)

I = (8/3) Ampere

So,
Resistor 1:
Resistor(R)= 3 Ohm
Voltage Drop(V) = 12 Volts
Current(i) = 4 Amperes

Resistor 2:
Resistor(R) = 6 Ohm
Voltage Drop(V) = 8 Volts
Current(i) = (4/3) Ampere

Resistor 3:
Resistor(R) = 3 Ohm
Voltage Drop(V) = 8 Volts
Current(i) = (8/3) Ampere
Fronzbot
#5
May9-10, 10:27 AM
P: 62
Err, fallen186, you may want to read the rules over real quick. Specifically this line:
Under no circumstances should complete solutions be provided to a questioner, whether or not an attempt has been made.
Cheesus128
#6
May9-10, 11:53 AM
P: 22
Quote Quote by Fronzbot View Post
Err, fallen186, you may want to read the rules over real quick. Specifically this line:
Whats the point of that rule?
Anyway back to fallen186īs answer.
Thank you.
That helped me as well.
Fronzbot
#7
May9-10, 11:54 AM
P: 62
Quote Quote by Cheesus128 View Post
Whats the point of that rule?
So the members here don't do your homework
Cheesus128
#8
May9-10, 11:57 AM
P: 22
Quote Quote by Fronzbot View Post
So the members here don't do your homework
Hahahaha that made me smile
Oh well every forum has its own rule.
But still its not like he is posting his whole paper or HW here, he is only posting one question so wouldnt that be something else?
I mean mostly you can only find how something works by knowing the answer and the exact way of getting there.
Hence you need the full explanation?
alan1592
#9
May9-10, 02:03 PM
P: 8
Yeah he was very helpful to me too. I deff learned how to do the problem and thats what i wanted. Thanks man!


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