[Physics] Question about oersted’s experiment

electromagnetism

So I was studying my physics notes. They are on the magnetic field shown by a straight current carrying wire. To demonstrate that theres the oersted's experiment. The starting goes like this-

Insert a thick copper wire between 2 points, X and Y, in a circuit. The wire should be perpendicular to the plane of paper. Place a compass horizontally to the wire. Switch on the current. The compass needle shows deflection

My question is – what does placing the wire XY perpendicular to the plane of paper mean?

And why would you do that? Please help.

Best Answer

“The paper” is probably just meaning the table. So let's put the wire vertically going in the up-down direction. Using the right-hand-rule we obtain that the magnetic field will be circles in the plane of the table/paper.

The compass will align itself to the magnetic field lines. Therefore the rotating compass should be positioned such that it points towards the wire or parallel to it. When you turn on the magnetic field, it can align itself with the magnetic field lines.

Take a look at some video of the experiment. There you can see that the magnet will align itself perpendicular to the wire and parallel to the plane that the wire is perpendicular to (that sentence is probably unnecessarily complex).