Register to reply 
Two circuits connected by a single wire, will there be current in wire? 
Share this thread: 
#1
Aug2911, 01:43 PM

P: 248

If 2 circuits are connected by a single wire, will there be current in the wire?
If there is current, it can only goes throgh one way (ex: right or left) . In a 2 circuits like the example, Where c and d are generators, e/f/g resistors. The wire AB is inicially unplugged and then plugged. In which case of voltage of the generators/resistance of the capacitors There would be current i n AB and in which case there wouldn't be? What would happen if c or d were capacitors? 


#2
Aug2911, 01:47 PM

P: 146




#4
Aug2911, 01:51 PM

P: 882

Two circuits connected by a single wire, will there be current in wire?
@Vortex
But, if you have all components values? OK. Take: c: 4.5V, d: 9V, f: 100ohm, e: 300 ohm, g: 1000 ohm. Could you tell us now what will be a currend AB and which direction? 


#5
Aug2911, 02:02 PM

P: 882

@jaumzaum: nothing happens. Maybe small current flows for a very short while just after you connect A and B  discharging their initial difference in potentials (that would be equivalent to an initially charged capacitor connecting those halves).
Current always flows along some loop  AB do not form one. 


#6
Aug2911, 07:18 PM

P: 248

Thanks xts
And why the current is small (or almost none) in AB? How can we calculate it? Will there be ac urrent until the 2 circuits get the same potencial difference? 


#8
Aug3011, 05:42 PM

Mentor
P: 17,224

There is no current. You can analyze with node voltage or loop current, my preference is node voltage.



#9
Aug3011, 05:51 PM

P: 248

Thanks Dalespam
I already know theres no current (its a question I've already s een before) I want to know why 


#10
Aug3011, 05:53 PM

Mentor
P: 17,224

Just use standard analysis techniques like node voltage:
http://people.ee.duke.edu/~gary/ECE27/nvm.pdf 


#11
Aug3011, 05:55 PM

P: 5,462

I think this is a trick question.
What happens if you redraw it thus? 


#12
Aug3011, 07:26 PM

P: 248

In G: R3.i1 + R1.i1 V1 = 0 > i1 = V1/(R1 + R3) In H: R2.i2 + V2 = 0 > i2 = V2/R2 i1 = i2 + i3 > i3 = V1/(R1 + R3)  V2/R2 But what that thing has to do with the other? 


#13
Aug3011, 08:14 PM

Mentor
P: 17,224




#14
Aug3011, 10:09 PM

P: 248

I didn't understand?
I'm still getting i3 = V1/(R1 + R3)  V2/R2 Couldn't you solve it? My test is in 2 days, and I have a lot of things I wanted to ask too I would be thankful []s John 


#15
Aug3111, 02:07 AM

P: 1,396

The current through the first AB wire is obviously 0 because there is no return path. If there was a current, electrons would pile up on one side, creating a potential difference, that would stop the current. 


#16
Aug3111, 06:20 AM

P: 280




#17
Aug3111, 06:50 AM

Mentor
P: 17,224




#18
Aug3111, 06:53 AM

Mentor
P: 17,224




Register to reply 
Related Discussions  
Current carrying wire and induced electric field within the wire  Introductory Physics Homework  2  
Total charge through point on wire due to changing current on other wire  Advanced Physics Homework  1  
Wire Loops, Current, Magnetic Field, & Straight Wire HELP!  Introductory Physics Homework  1  
0.5V across 1.5m tungsten wire w/crosssect. area 0.6 mm^2  Find wire current  Introductory Physics Homework  3  
Circuits: ThreeWire Single Phase System  Engineering, Comp Sci, & Technology Homework  0 