



Full Member


Nov 15, 2011, 12:35 PM


Find the electrical potential difference
Given electrical network (in the picture).
I asked to find the electrical potential difference between A and B. UAB
I tried and not find the answer.
I really need help.
Thanks.



Uber Member


Nov 15, 2011, 12:43 PM


Where is the picture? I don't see one.



Full Member


Nov 15, 2011, 12:47 PM


Oh sorry.
Here is it



Expert


Nov 15, 2011, 01:12 PM


Start by finding the equivalent resistance that can replace the 4ohm, 3ohm, and two 6ohm resistors. What do you get for that resistor? That equaivalent resistor splits the battery voltage in conjunction with the 3 ohm reistor on the left. Post back with what you get for an answer.



Full Member


Nov 15, 2011, 01:52 PM


well I find the equivalent resistance that can replace the 6 ohm and the 3 ohm (they are parallel) so I get:
6*3/(6+3)=2ohm.
and I get a new electrical network (in the picture).
my big problem is how to keep from this point, I know there is a law that helps in this kind of problem (I not sure how is call in english), maybe is call a Converting triple star.
thanks.



Expert


Nov 15, 2011, 02:02 PM


Remember that resistors in parallel don't add  you must use the formula:
Hence the 3ohm and 6ohm resistors in parallel are equivalent to:
ohms.
Next step is that this 2ohm resistor plus the 4ohm in series adds to 6 ohms, which is in parallel with the remaining 6ohm resistor.
Can you take it from here?



Full Member


Nov 15, 2011, 02:17 PM


yes I get 6 ohms which is in parallel with the remaining 6ohm resistor so is equal to 6*6(12)=3ohms
and this equivalent resistance is series to the last 3 ohms resistor and I get RT=6 ohms
then I do E=6V/RT so I get 6/6=1v Uab=1v
do I correct ?



Expert


Nov 15, 2011, 02:28 PM


You have RT = 6 ohms which is correct. But voltage divided by resistance is current, not voltage. From Ohm's Law:
V=IR,
6 volts = I * 6 ohms,
I = 1 amp.
Now you can use use Ohm's Law again to find the voltage drop across the 3ohm resistor that spans points a and b:
V = IR = 1 amp x 3 ohms = ? Volts



Full Member


Nov 15, 2011, 02:39 PM


Oh yes you correct.
But I have to ask why u took the 3ohm resistor voltage that spans points a and b:
And not the 6 ohms resistor that also spans points a and b ?



Expert


Nov 15, 2011, 03:01 PM


Yes  I made an error  sorry! The progression of how we got from your original circuit diagram to two 3ohm resistors in series is shown in the figure below. The current around the circuit is 1 amp. But only half of that goes through each of the 6 ohm resistor equivalents. So the voltage drop across ab should be V = IR = 1/2 amp x 2 ohms = 1 volt.



Full Member


Nov 15, 2011, 03:06 PM


wow you made is clear now :) now I understand it.
so as u told beofoe V = IR = 1 amp x 3 ohms = 3 volts
so this is the final answer Uab=3v ?



Full Member


Nov 15, 2011, 03:07 PM


*made it



Expert


Nov 15, 2011, 03:34 PM


Originally Posted by pop000
wow you made is clear now :) now i understand it.
so as u told beofoe V = IR = 1 amp x 3 ohms = 3 volts
so this is the final answer Uab=3v ?
After I made my previous post I realized I had an error, so was in the midst of correcting it when you posted. Sorry for the confusion.



Full Member


Nov 15, 2011, 03:41 PM


that OK :) .so you can tell me if the final answer is Uab=3v?
thanks so much for your help and for your time.



Expert


Nov 16, 2011, 09:18 AM


Originally Posted by pop000
that ok :) .so you can tell me if the final answer is Uab=3v?
No  1/2 amp of current flowing through a 2 ohm resistor yields? Voltage drop across that resistor.



Full Member


Nov 17, 2011, 01:01 AM


Ok now I got it.
Thank you very much.


Question Tools 
Search this Question 


Add your answer here.
Check out some similar questions!
Potential difference, Current, Resistance
[ 1 Answers ]
A source of variable potential difference is attached across the ends of 1 m of resistance wire and the potential difference across the wire is steadly increased.
a) Describe how the current through the wire changes
b) Provide the temperature of the wire does not change significantly, what radio...
Potential difference
[ 2 Answers ]
protons and electron are placed at point x=1cm, 3cm 5cm & x=2cm,4cm,6cm respectivelyon xaxis up to infinity what is potential difference origin
How to find potential energy
[ 1 Answers ]
Suppose an Olympic diver who weighs 52.0 kg executes a straight dive from a 10m platform. At the apex of the dive, the diver is 10.8m above the surface of the water.
a) What is the potential energy of the diver at the apex of the dive, relative to the surface of the water?
b) Assuming that all...
I want to know actually potential difference is ?
[ 2 Answers ]
Is it just like diffusion gradient which results in osmosis or is it something else? Moreover also when we go accroding to ohm's law current is directly propertional to potential difference, but our teacher today taught us power transmission and he said
P=VI in which if V is more then I is loss...
Potential difference
[ 1 Answers ]
Calculate the potential difference across each resistor in parallel. 12v dc supply, 10 ohms (R) 5 ohms(R)?
View more questions
Search
