Understanding Alternating and Direct Current
Direct Current flows in one constant direction with a fixed polarity. The voltage remains constant over time.
V(t) = Vconstant (e.g., 5V, 12V)
Alternating Current periodically reverses direction, creating a sinusoidal waveform. The voltage oscillates between positive and negative values.
V(t) = Vpeak × sin(2πft)
where f = frequency (Hz), t = time
RMS (Root Mean Square) Voltage:
VRMS = Vpeak / √2 ≈ 0.707 × Vpeak
Example: 120V AC RMS = 170V peak voltage
| Property | DC | AC |
|---|---|---|
| Direction | One direction | Alternates both ways |
| Frequency | 0 Hz (constant) | 50/60 Hz (varies) |
| Polarity | Fixed (+ and -) | Changes periodically |
| Transmission | Higher losses | Lower losses (transformers) |
| Storage | Easy (batteries) | Difficult (convert to DC first) |