Electric Shielding and Polarization

1
Electric Shielding and Polarization
2
Lightning

• Where is the safest place to be in a thunder
  storm?

3
A Car!!!

• Both of these cars where hit by lightning and
  nobody inside was injured by the lightning.
• Why is a car safe?

4
Lightning safety in a car

• The tires are not what make you safe
• The shell of a car in a thunder storm is made of
  wet glass and metal which are good conductors
• Therefore you have electrical shielding
• This is called a Faraday Cage

5
Electric field inside a conductor

• The electric field inside a conductor will be
  zero even if the conductor is in an electric field

6
Facts about electrical shielding

• Used to protect sensitive electronic equipment
• Shielding is not possible with gravity since it
  is only an attractive force

7
Polarization on a conductor

• On a conductor electrons are free to move
• When a charge is brought near a conductor it will
  attract or repel electrons
• This causes a positive charge on one end and a
  negative charge on the other

8
Polarization on an insulator

• Electrons on an insulator are free inside each
  atom, but not among the atoms
• When a charge is brought near an insulator it
  will attract or repel electrons, causing each
  atom to be polarized

9
Balloon on a wall

• The charged balloon polarized the atoms of the
  wood
• Once the atoms in the wood are polarized, the
  negative charge of the balloon attracts the
  positive charge near the surface
• The balloon sticks to the wall

10
Quick Facts about Polarization

• Polarization is NOT charging, the overall charge
  of the object does not change
• Polarization is used to charge by induction

• Polarization is what allows a charged object to
  attract a neutral object