Book 3, Question 46
Why Do Power Lines Hum?
Power lines carry alternating current, which rushes back and forth in the wire. In many countries, it flips direction 60 times every second. In others, it's 50 times!
From the book
Page from A Million Whys Book 3
More fun facts
- The buzz near high-voltage power lines comes from something called corona discharge around the wires.
- Corona discharge can also cause radio static and even a faint glow of light near the wire.
- Power lines get louder in rain, drizzle and fog, because water helps the air carry electricity.
- Nicks, sharp points and dirt on a wire can make the crackling stronger.
- Modern lines are designed to stay nearly quiet in dry weather.
- The U.S. power grid runs at 60 hertz, which means the electricity swings back and forth 60 times every second.
Sources: Scientific American, U.S. Department of Energy
Questions kids ask
Why are power lines noisier when it rains?
Water helps the air around the wire carry electricity, which makes the crackling corona discharge stronger.