Why Do Two Magnets Repel?

    • We've all seen it: try to press the same pole of two magnets against each other, and there's a repellent force driving the two magnets apart. To completely understand why, precisely, magnets do this is a complicated endeavor---asking any physics major about her E&M class will invariably result in a number of horror stories---but the basics of why this happens can be grasped easily if you understand a few things about magnets.

    Electromagnets

    • Perhaps the most utilized magnet in industry is the electromagnet. These magnets, seen in car-wrecking lots attached to cranes, are magnetic because of the flow of electricity through a circuit. Electricity, of course, is caused by electrons jumping from atom to atom in a circle we refer to as a circuit. All circuits have a directional magnetic field, caused by this movement of electrons through the wire. Electromagnets concentrate this field in one place, often by densely coiling a wire and running electricity through it, creating a strong magnetic field---in the case of junkyard cranes, strong enough to lift cars.

    What Magnets Attract

    • It should also be noted that magnets attract only certain elements such as iron, cobalt and nickel. These elements can be attracted to magnets because of an unpaired electron in the element's outer orbits. These electrons tend to align with magnetic fields, which when spread throughout an entire piece of metal cause the metal to pull toward the magnet, as if it were a magnet itself.

    Magnets

    • Magnets themselves also have this unpaired electron---its alignment is simply frozen in a particular direction rather than responding to the field of another magnet. Any of the elements that are attracted to magnets can actually become temporary magnets, if exposed to magnetic force long enough. This is because being exposed to magnetic force aligns electron spin in a certain direction. When this happens, a north and a south pole are created at the side toward which the electrons point and the opposite of this side; because of the alignment of the electrons, these two points are the most powerful points in the magnet.

    Repel

    • By understanding the forces behind magnets attracting certain metals, you can now understand why two magnets push against each other. The alignment of the magnet creates a magnetic field with a north and south pole: north poles are attracted to south poles, but like poles repel. Two north poles or two south poles will invariably push against each other. So the very force that causes magnets to be attracted also causes like magnets to push against each other. Simply put, if electrons are leaning one way in one magnet, that magnet will push against another magnet leaning against it.

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