When a conductor (like a copper wire) moves through a magnetic field, or when the magnetic field around a conductor changes, an electric current can be produced in the conductor. This is known as electromagnetic induction and is the principle behind many everyday devices such as electric generators and transformers.
Think of a magnet as a roller‑coaster track. If you slide a metal train (the conductor) along the track (the magnetic field), the train feels a force that pushes it forward or backward. That force is actually an electric current being generated in the train’s metal body.
The LED lights because the moving magnet changes the magnetic flux through the coil, inducing a current that powers the LED. When the magnet moves away, the flux decreases, and the induced current reverses direction.
| Symbol | Meaning | Units |
|---|---|---|
| \$\Phi_B\$ | Magnetic flux through a surface | Weber (Wb) |
| \$B\$ | Magnetic flux density (field strength) | Tesla (T) |
| \$A\$ | Area of the surface | m² |
The flux is calculated as \$\Phi_B = B \times A \times \cos\theta\$, where \$\theta\$ is the angle between the magnetic field direction and the normal to the surface.
Imagine a roller coaster track (magnetic field) and a metal car (conductor). When the car moves along the track, the magnetic forces push it, creating a current in the car’s wheels. If you change the track’s shape or speed, the current changes accordingly. This is exactly what happens in a generator.
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