Hi !!! First - my apologies, I'm a physics "newbie" and my question may sound quite "stupid" to most of the people here but I'm just wandering about something and hope you can help me - to understand why/if this is true or false. Say we have a beam of electrons pointed right into the middle of a source of magnetic field. One of the magnetic poles is "+" and the other is "-". The electrons from the beam should "bend" towards the positive pole since they have negative charge. I believe this was how they were discovered but may be mistaken. So my question is - how you can 'know' which magnetic pole 'exerted' more force - the positive one - due the attraction with the negative charge of the electrons or the negative one - due the repelling force because of the same charges ? Does the beam bends because of the "+" magnetic pole attraction or due the "-" magnetic pole repulsion ? I know that this sounds kind of philosophical and may not matter in the "real world" - say it does :) how you can know which pole is the 'reason' for the bending ? And can you know this at all ? Of course I assume "perfection conditions" which imply that you are actually able to point the electron beam right into the "middle" of the source of magnetic field. Thanks in advance !