Help for direct current circuit

[Primarygun]

Please have a look at the photo below. Thanks

Referring to the figure, I tried to find out the current flowing in AB so as to solve it. However, I was not able to finish it as planned.

Can anyone give a brief note on the solution?

Moreover, I have some questions in my mind.

1. Can a current flow through in this sequence, DABE can CBAE?

If yes, then the two currents meet in the branch AB with opposite direction.

Will a problem arise?

2. Can a current pass through a particular junction two times?

Thanks.

[Edit] Important: Please neglect the question in the photo.

Here is the question: Find the reading of the ammeter in terms of E(Emf/V) and R

[YT2095]

Hmm.. basicly it`s a wheatstone bridge just drawn a little differently

 

have a look here: http://www.hvacmechanic.com/whetstone_bridge.htm

this should help a little.

[Kedas]

Just apply Kirchhoff's law's or if you don't know that assuming that the resistance of the A-meter is zero you can just connect the two then AE and BE have the same voltage same for the other side so you can calculate the current of all resistors and the one that goes through the A-meter is the one that makes the total current in point (A or B) equal to 0.

 

Currents can't flow in the two direction at the same time but when you applying Kirchhoff's you don't need to know the right direction just guess one if it's the wrong direction then the calculated current wil just be negative (meaning not flowing in the direction of the arrow)

[5614]

Don't you measure the p.d across a battery and not the e.m.f ?

 

I mean I know the difference, but isn't a battery the exception to the rule of when to use pd opposed to emf?

[Primarygun]

Just apply Kirchhoff's law's or if you don't know that assuming that the resistance of the A-meter is zero you can just connect the two then AE and BE have the same voltage same for the other side so you can calculate the current of all resistors and the one that goes through the A-meter is the one that makes the total current in point (A or B) equal to 0.

Besides Kirchhoff's law, which laws are still important to elementary circuit?

The law is not required to learn for me, but I'd like to learn more though.

 

I could figure it out the solution by considering the right part only first.(cover the left part)

Find the equivalent resistance, then open the left part, a // circuit.

Find the current in the main branch. Since ammeter has no resistance, all currents are drawn to it. so that's the answer, right?

Although I may find out the solution later with the powerful law suggested by you guys,

but I'm afraid I still won't know the solution to my own questions.

May you please tell me ?

1. Can a current flow through in this sequence, DABE can CBAE?

If yes, then the two currents meet in the branch AB with opposite direction.

Will a problem arise?

2. Can a current pass through a particular junction two times?

Thanks.

[Kedas]

1. Can a current flow through in this sequence' date=' DABE can CBAE?

If yes, then the two currents meet in the branch AB with opposite direction.

Will a problem arise?

[/b']

Yes, a big problem will arise be very careful when making that circuit particles will collide and a nuclear explosion can occur. (see my previous post)

 

If you want to do the left side first and then the right side then you can make a Thevenin equivalent circuit of the left part and also the right part and then connect them and calculate that current (this is your A-meter current).

 

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/thevenin.html

you can find all basic info here:

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/dccircon.html#c1

[5614]

1. Can a current flow through in this sequence, DABE can CBAE?

If yes, then the two currents meet in the branch AB with opposite direction.

Will a problem arise?

The current will not flow both ways at once, obviously that would run into problems. For a current to flow through AB you'll need a potential difference (pd) across it, if you look at the diagram one of the resistors has value 2R. This effects the pd along the potential divider (2 resistors) this will alter the voltage at point A (ie. if all resistors were value R then there'd be a 0V pd across AB), however due to the 2R value of one of the resistors voltage at A will be different to voltage at B so a pd will be present meaning a current in a specific direction.

 

2. Can a current pass through a particular junction two times?

What do you mean?

 

If you think of a circuit with a junction and you leave it on for long enough current will pass through that junction many times as it goes around the circuit many times. Or do you mean can it go backwards and forwards? In which case AC would, whereas DC wouldn't.

[Primarygun]

If you think of a circuit with a junction and you leave it on for long enough current will pass through that junction many times as it goes around the circuit many times. Or do you mean can it go backwards and forwards? In which case AC would, whereas DC wouldn't.

Sorry, I mean if a current pass through 1 and, will it be possible for it to pass through this node in opposite direction?

For a help please, Iab=Ibe=Iad=Iae?

[5614]

Sorry' date=' I mean if a current pass through 1 and, will it be possible for it to pass through this node [b']in opposite direction?[/b]

For a help please, Iab=Ibe=Iad=Iae?

 

I still don't understand what you mean!

 

A current cannot go in 2 directions through one junction, as that is like opposite current down 1 wire, it's impossible.

 

To get a current flowing in both directions at once you'd need e.g one end of the junction to have a positive voltage and the other end to be positive (relative to the other) so you have one side positive compared to the other and the other side is positive compared to the 1st, it doesn't work. Like +3V and +6V because then you have a pd of 3V so a current goes from the 6 to the 3 which is totaly identical to 3V and 0V..... and if you have like +6V on both sides then you'd have a potential difference of 0V so no current.

 

If you reverse the voltages then the current will change direction, so if you switch the polarit of the battery or had an AC power supply.

 

You say a "node" by that I assume you mean the split from 1 wire into 2 wires (or more) ie. a junction. As a junction is just wires (1 or 2 or 3 or more, no difference) all above still applies.

 

Does that help?

[Primarygun]

With you guys' helps, including richard's, I was able to find it out.

I could find out 3 methods of getting the answer.

Namely, Delta one, Equation one, splitting one.