120-volt power, as typically found in wall outlets in the United States, is AC (Alternating Current).
Understanding AC vs. DC
To understand why 120-volt power is AC, it's helpful to know the difference between alternating current (AC) and direct current (DC):
- Alternating Current (AC): The flow of electric charge periodically reverses direction. This means the voltage also periodically reverses. The standard AC voltage in US wall outlets is 120 volts, alternating at a frequency of 60 cycles per second (60 Hz).
- Direct Current (DC): The flow of electric charge is only in one direction. Batteries are a common source of DC power.
Why AC for Power Distribution?
The primary reason AC is used for long-distance power transmission is the ease with which its voltage can be changed using transformers.
- Transformers: These devices efficiently increase or decrease AC voltage. This is crucial because transmitting electricity at high voltage over long distances minimizes power loss due to resistance in the wires. The voltage can then be stepped down to safer levels (like 120 volts) for use in homes and businesses.
Key Differences Summarized
| Feature | Alternating Current (AC) | Direct Current (DC) |
|---|---|---|
| Current Direction | Reverses periodically | Flows in one direction only |
| Voltage | Changes polarity | Constant polarity |
| Voltage Change | Easy with transformers | Difficult |
| Common Sources | Wall outlets | Batteries |
In conclusion, the 120-volt power supplied to homes and businesses in the United States is alternating current (AC), primarily because AC voltage can be easily transformed for efficient long-distance transmission.
