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Why does…?

Why Does That Happen? — Everyday electricity questions answered in 30 seconds.

3 of 10 lessons out · next: Why do LED bulbs last so much longer than old bulbs?

▶ Start lesson 1
  1. 01 Why don't birds get shocked on power lines?both feet on one wire = no voltage difference across the bird → no current. EP.60 · 24 s
  2. 02 Why does your phone get hot while charging?the charging chip and the battery's internal resistance turn some energy into heat (I²R); fast charging = more current = more heat. EP.66 · 24 s
  3. 03 How does a microwave heat your food?2.45 GHz waves twist water molecules back and forth billions of times a second → friction heat. EP.72 · 24 s
  4. 05 PLANNEDWhy does your phone battery die faster in the cold?the lithium-ion chemistry slows down, internal resistance rises, the voltage sags.
  5. 06 PLANNEDHow does a metal detector find metal?a coil makes a changing magnetic field, metal answers with eddy currents that a second coil picks up.
  6. 07 PLANNEDWhy do transformers hum?the iron core changes size slightly 100 times a second on 50 Hz mains (magnetostriction) → a 100 Hz hum.
  7. 08 PLANNEDWhy do power lines use such high voltage?same power at higher voltage = less current, and line loss = I² × R.
  8. 09 PLANNEDHow does your TV remote talk to the TV?an infrared LED blinks codes on a ~38 kHz carrier; your phone camera can see it.
  9. 10 PLANNEDWhy do you see a spark when you pull a plug out?the current tries to keep flowing (inductance) and jumps the tiny air gap as an arc.