Electricity

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   Benjamin Franklin is often credited with "discovering" electricity.  That's a huge thing to get credit for just by flying kites.  If you agree with giving him credit then electricity celebrates it's 269th birthday this year.

   One thing about electricity you might now know:  anytime electricity flows through a wire it creates an electromagnetic field. So there's usually a magnetic field around:

• Wiring in a home, workplace, or car.
• The wiring harness in a car.
• Power lines

   At least there is when the power is flowing.

   Because of that almost any electronic device near those things can build up and retain some charge.  It's through induction and it's the basis for charging wireless devices.

• Wireless power transfer on Wikipedia
• Inductive charging on Wikipedia

   Even when they're turned off.

   This means a person walking beside (or under) power lines carrying their cell phone might notice something strange.

   Someone's voice might seem to be speaking from the phone.  Not from the speaker and not necessarily from the display.  But from the plastic case containing the phone's electronics.  Glass backings to phones aren't as susceptible so it's rare when they're the culprit.

   You might be wondering if it matters whether the phone is turned ON or OFF.

   The answer to that is somewhat backwards.

   It makes no difference whether the phone is ON or OFF.

   Instead... you probably should be wondering whose voice you're hearing.