A magnet is an object that generates an invisible field of force around itself, a phenomenon known as magnetism. This force arises from the synchronized motion of electric charges within the material, even down to the atomic level of electron spin. Every complete magnet inherently possesses two regions where this magnetic force is concentrated and strongest, which are called the magnetic poles. These poles are universally designated as North and South, and they always exist in pairs, meaning you can never isolate a North pole without its corresponding South pole.
The Immediate Result
When you bring the North pole of one magnet near the North pole of a second magnet, you immediately feel a powerful resistance—a repulsive force attempting to increase the distance between the two ends. The magnets will resist your effort to push them together, feeling almost as if there is a spring between them. If you release the magnets from a short distance, they will accelerate away from each other until the magnetic field weakens. Like poles, such as North and North, or South and South, will always repel one another.
The Physics of Pole Interaction
The repulsion felt between the two North poles results from how their magnetic fields interact. A magnetic field is visualized using field lines, which emerge from the North pole and loop back to the South pole. When two North poles are placed in proximity, the field lines coming out of both poles travel in the same general direction. These lines push against and run parallel to one another, creating a region of high energy density between the poles.
Because magnetic field lines never cross, they are forced to bend away from the space separating the magnets. The lines act as if they are under tension and want to shorten their length, which results in the repulsion of the poles. This pushing action is the physical manifestation of the magnetic field attempting to reconfigure itself into a lower-energy state. The magnetic force pushes the two magnets apart to relieve the built-up magnetic pressure.
How Distance Affects the Force
The repulsive force experienced between two North poles is highly dependent on the distance separating them. The strength of the magnetic force decreases dramatically as the distance between the magnets increases. When the poles are nearly touching, the repulsive force is at its maximum, making it difficult to overcome. Even a small increase in separation causes the force to weaken significantly.
This rapid decrease occurs because the magnetic field lines spread out and become less dense away from the magnet. For simple magnets, the force follows an inverse square law. Doubling the distance between the poles reduces the force to about one-quarter of its original strength. The powerful push only exists in the immediate vicinity of the magnets, quickly fading as the poles separate.
Practical Uses of Repulsion
The consistent nature of magnetic repulsion is harnessed in several real-world technologies to eliminate friction. A famous example is in magnetic levitation (Maglev) train systems. These systems use powerful magnets to suspend the train car above the track, utilizing the repulsive force to create a frictionless lift. This levitation allows the train to reach extremely high speeds with minimal energy loss.
Magnetic repulsion is also a central component in devices like magnetic bearings and dampers. In these applications, the repulsive force holds rotating parts apart, replacing traditional physical contact bearings. Eliminating contact removes wear and tear, allows for higher operating speeds, and reduces the need for lubrication and maintenance. The principle of like poles pushing each other away provides a mechanism for non-contact support and motion.