Circuit Analysis

Discussion in 'Homework Help' started by robertli95, Nov 22, 2014.

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1. robertli95 Thread Starter New Member

Nov 22, 2014
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Hi Guys,

I just don't know why the current does not flow through branch A.

Thank you a lot, i am still a beginner here.
I receive any feedback and suggestion.

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2. ericgibbs AAC Fanatic!

Jan 29, 2010
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hi Rob,
Who says, no current flows thru path 'A'.?

Is that 4.5Amps a current source.? if yes, which way is the current direction.?

E

3. robertli95 Thread Starter New Member

Nov 22, 2014
3
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I tested it through simulator. the device that shows 4.5 amps is the ammemeter, i used it to measure the current of the circuit

4. ericgibbs AAC Fanatic!

Jan 29, 2010
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394
hi,
This circuit is drawn in LTSpice simulator, check that its the same as yours.
The R7 is a very low value so it will not affect the circuit, its only there so I can show you the 'A' current.
I dont get the same as you.?

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5. robertli95 Thread Starter New Member

Nov 22, 2014
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but i thought if the resistance is very low, then the current will be likely flow through it. Why you add R7 = 0.0001 there?

6. ericgibbs AAC Fanatic!

Jan 29, 2010
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I did tell you its ONLY there so that the Simulator can measure the current in path A, it will only slightly affect the analysis.
Is my circuit the same as yours.?

E
EDIT:
I have a drawing error in my first circuit, this is the correct version

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7. JoeJester AAC Fanatic!

Apr 26, 2005
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Once you redraw the circuit, you should see there is current flow in line A. This begs the question of where you got that circuit drawing?

I don't know how you got ONLY 4.5 amperes on that meter.

Below is my version of your original and my redrawing of the original. Clearly there is current in what is identified as Branch A ... where I placed the AM2 current probe.

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8. LDC3 Active Member

Apr 27, 2013
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I think everyone still has the wrong circuit. If the 2 ohm resistor is not connected to the negative post of the battery, there is no current flowing in branch A.

9. t_n_k AAC Fanatic!

Mar 6, 2009
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It looks connected to me but you could be correct - given the questionable schematic representation.

10. ericgibbs AAC Fanatic!

Jan 29, 2010
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Looking at the TS diagram, it shows a dotted ring around each junction, so it looks as though the 2R is connected.?
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11. ScottWang Moderator

Aug 23, 2012
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According your first circuit, the current will flows through A wire, but the current is not 4.5A, it's more than that.

12. LDC3 Active Member

Apr 27, 2013
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160
I did a simulation with and without a connection of the 2 ohm resistor connected to the negative post of the battery. Here is a link to the simulation.
With the connection, the current through the battery is 11.25 A and the current through branch A is 4.5 A.
Without the connection, the current through the battery is 4.5 A and there is no current through branch A.

Last edited: Nov 23, 2014
13. JoeJester AAC Fanatic!

Apr 26, 2005
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I think it does.

I also think the OP needs to clarify the circuit by cleaning it up or redrawing it by hand.

I agree with Eric ... the connections are indicated as he stated. Here is the diagram with the component connections circled in yellow.

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