Take the wire on the right hand side. It experiences a force to the left of the page. To experience a force pointing left-wards, the magnetic field must point into the page. Why does it point into the page, given that magnetic field tangents run in all directions from the circular field?? If we identified exclusively one direction of travel, B could point rightwards as much as it does point into the page.

I understand the right hand rule used to determine the direction (clockwise or cccw) of the magnetic field around a current-carrying wire. In the given diagram, the field lines run counterclockwise, but I can't identify a justification for choosing a field line that points into the page.

Magnetic Field around current carrying wire


1 Answer 1


The force on the right hand wire comes from the magnetic field originating from the left hand wire, not the magnetic field from itself. This magnetic field hits the right hand wire in only one direction, names into the page. Hence, the force on the right hand wire points in one direction.

  • $\begingroup$ sorry if I misled you. I meant to ask: why does the magnetic field line point INTO THE PAGE? I didn't question the validity of any RHR, but why one magnetic field direction could be separated from the infinite number of field directions (given by tangents) that exist $\endgroup$
    – Muno
    Feb 1, 2015 at 21:20
  • $\begingroup$ I edited the answer $\endgroup$
    – user70720
    Feb 1, 2015 at 21:35

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