Electricity and Magnetism United
Magnetism and electricity, once thought separate, are two aspects of one electromagnetic force. This unification powers modern technology from hard drives to Wi-Fi.
| Phenomenon | Description | Application |
|---|---|---|
| Current to Field | Moving charges create a magnetic field circling the wire. | Electromagnets |
| Field to Force | Magnetic fields exert a force on moving charges perpendicular to both. | Electric motors |
| Induction | Changing magnetic fields induce a voltage in a nearby loop. | Generators |
Maxwell's synthesis proved that oscillating electric and magnetic fields sustain each other and propagate as electromagnetic waves, which includes all light and radio signals.
Faraday's Law and Induction
Electromagnetic induction relies entirely on change. A steady, motionless magnetic field induces zero voltage or current in a loop.
The induced voltage depends on the rate of change of magnetic flux through the circuit. Faraday's law dictates that motion or variation is strictly required.
| Field State | Effect on Circuit |
|---|---|
| Steady / Motionless | Zero current / no induction |
| Changing / Moving | Current induced |
Common pitfall: Thinking a steady magnetic field induces a current. Only a changing field does. A magnet sitting motionless near a coil induces nothing; the current appears only while the field changes.