DC and AC Current #
Two fundamental types of electric current: Direct Current (DC) — flows in one direction — and Alternating Current (AC) — oscillates back and forth sinusoidally.
DC: constant direction and magnitude. Produced by batteries, solar cells. Used in electronics, smartphones, electric cars. #
AC: changes direction periodically (50 Hz in Europe, 60 Hz in USA). \(V(t) = V_{max} \cdot \sin(2\pi f \cdot t)\). Produced by generators. Used in the power grid, home appliances, industry. #
Why AC Won #
AC can be transformed easily: step up voltage for long-distance transport (less losses), step down for home use. Edison (DC) lost to Tesla/Westinghouse (AC) in the “War of Currents.”
Conversion #
- AC → DC: rectifier (diode bridge) — e.g., phone charger
- DC → AC: inverter — e.g., solar panels to grid
| Feature | DC | AC |
|---|---|---|
| Direction | One way | Alternating |
| Graph | Flat line | Sine wave |
| Long-distance transport | Difficult | Easy (transformers) |
| Main sources | Batteries, solar panels | Generators, grid |
Conclusion #
DC for electronics and batteries, AC for power distribution. In practice, both coexist and are constantly converted from one to another.
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