Magnetic field and parallel current-carrying wires

[ah4p]

could someone explain question 10. JUST PART b)iii)

http://mrmackenzie.wikispaces.com/file/view/AHpastpaper2004.pdf

I got the magnitude of the magnetic field
but I don't know how to find its directionI thought it might be to do with left and right hand rule?

the answer is upwards
could someone please explain why this is so?

thank u v much in advance :)


[Moderator note: Moved to new thread; removed bits of old thread from this post]

 

[Doc Al]

could someone please explain why this is so?

How would you apply the right hand rule to find the direction of the magnetic field around a current-carrying wire?

 

[ah4p]

How would you apply the right hand rule to find the direction of the magnetic field around a current-carrying wire?

I don't know

using the left hand rule (I'm Scottish so I use negative current) surely the magnetic field due to one wire is up and due to the other one is down so they'd cancel?

 

[Doc Al]

I don't know

using the left hand rule (I'm Scottish so I use negative current) surely the magnetic field due to one wire is up and due to the other one is down so they'd cancel?

It does say electron flow, so you're good with a left rule. (Although I recommend always using a right hand rule and positive current.) Realize that the current in each wire goes in opposite directions. Describe the direction of the magnetic field surrounding each wire.

 

[ah4p]

It does say electron flow, so you're good with a left rule. (Although I recommend always using a right hand rule and positive current.) Realize that the current in each wire goes in opposite directions. Describe the direction of the magnetic field surrounding each wire.

one goes into the page and one out of the page?

thanks for your help :)

 

[Doc Al]

one goes into the page and one out of the page?

Nope! Try again. ;)

 

[Doc Al]

Note: It's not completely clear which wire is closest to the viewer. I will assume that the wire appearing lowest in the diagram is closest to the viewer. (Use whatever makes sense to you, just state what assumptions you are making.)