Confused About Right Hand Rule: Understanding Magnetic Fields

[lha08]

Homework Statement

I'm so confused about how to use the right hand rule..there are so many different sources telling me different things...like i need to use the RHR to like find the direction of the magnetic field using the current (and nothing else)..like i followed my book, and they said to use my thumb to point towards the current and wrap my fingers around the wire as if i was holding it in my hand, and the direction of the wrapped fingers would give the direction of the magnetic field, but everytime i do it for a question or something, even though the current is in the same direction, some questions tell me that the Magnetic field is in 2 complete different directions...like one will say the the M. field is out of the paper and the other into the paper even though the current is flowing in the exact some direction...help!

Homework Equations

The Attempt at a Solution

 

[Doc Al]

Realize that the magnetic field forms concentric circles around the current-carrying wire. So, if current is moving from right to left (in the plane of the paper) then the magnetic field points into the page above wire and out of the page below it. See: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c1"

 

[lha08]

Realize that the magnetic field forms concentric circles around the current-carrying wire. So, if current is moving from right to left (in the plane of the paper) then the magnetic field points into the page above wire and out of the page below it. See: http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magcur.html#c1"

But like when we solve problems, is there a specific way to use the RHR that will tell us if it's coming or going in the page at a specific current even though it moves in a circle?
Like when you said that when the current is moving from right to left, what do you mean by 'the magnetic field points into the page above wire and out of the page below it'...?

 

[Doc Al]

But like when we solve problems, is there a specific way to use the RHR that will tell us if it's coming or going in the page at a specific current even though it moves in a circle?

You use it just like you (and the link I gave) describe. Try to picture the magnetic field lines as circles in three dimensions surrounding the wire. The field always points tangent to the circle in the direction given by the RHR. Then you have to determine what direction the field points where it touches the page.

Like when you said that when the current is moving from right to left, what do you mean by 'the magnetic field points into the page above wire and out of the page below it'...?

In that example, the wire is in the plane of the paper, so the magnetic field lines are circles perpendicular to the page. You must imagine how those field lines intersect the page. Where they touch the page above the wire, they are pointing directly into the page.

Take a look at Fig 28.6 on this page (down toward the bottom); it might help you visualize what's going on: http://www.physics.sjsu.edu/becker/physics51/mag_field.htm"