Magnetism Fundamentals

Spin a magnet inside a coil of copper wire and electricity comes out. That single fact is responsible for more than 99% of the world's electricity generation. Coal plants, gas turbines, nuclear reactors, wind turbines, and hydroelectric dams all ultimately spin a magnet inside a coil. The fuel changes; the mechanism does not.

Magnetism is a force produced by moving electric charges. In permanent magnets, the "moving charges" are electrons spinning within atoms. When enough electron spins align in the same direction (as they do naturally in iron, cobalt, and nickel), their tiny magnetic fields add up into a field strong enough to stick a note to your refrigerator. Every magnet has two poles, north and south. Like poles repel; opposite poles attract. You cannot isolate a single pole; cutting a magnet in half gives you two smaller magnets, each with both poles.

The energy connection is electromagnetic induction: when a magnetic field moves relative to a conductor (or vice versa), it pushes electrons through the conductor, creating electric current. This is how generators work. It is also how electric motors work in reverse: run current through a coil near a magnet and the coil spins. Generator and motor are the same device, used in opposite directions.

Worked Example

A simple generator spins a magnet at 60 revolutions per second inside a coil of wire, producing alternating current (AC) at 60 Hz (the U.S. grid standard).

• Identify the mechanism. The spinning magnet creates a changing magnetic field through the coil.
• The changing field pushes electrons back and forth in the wire.

Why does the current alternate (switch direction) rather than flow steadily in one direction?

Because the magnet's north and south poles alternate past each coil turn with every half-rotation. Each reversal pushes the electrons the opposite way. One full rotation produces one complete cycle, so 60 rotations per second produces 60 Hz AC.

The interaction between magnets and conductors is the physical foundation of every generator, motor, and transformer on the grid.

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