Everyday Electricity
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Transcript of Everyday Electricity
Everyday Electricity
February 26th, 2009
Conductors in Electrostatic Equilibrium Electrostatic equilibrium
When no net motion of charge is occurring within a conductor
Electrical field is 0 everywhere inside conductor Any excess charge resides entirely on the conductors
outer surface Electrical field just outside a charge conductor is
perpendicular to the conductor’s surface Charge tends to accumulate where the radius of
curvature of the surface is smallest (sharp points)
Why does it matter?
When a conductor is in electrostatic equilibrium charge will collect at the sharpest points
When enough
charge accumulates
it will suddenly
discharge
Van de Graaff Generator
The top of the generator
is a sphere so that large
amounts of charge can
build up without discharging
(they would discharge if
there was a point on top)
Static Electricity & Lightning
Lightning occurs because of a polarization of the storm clouds
The bottom of the cloud
develops an excess of
Negative charge A positive charge is
then induced on the surface
of the earth
As the static buildup during the storm becomes stronger the electrical fields around the cloud become strong enough to ionize the air, making it able to conduct electricity (becomes a conductive plasma)
A lightning bolt begins when a step leader of excess electrons begin to move towards the ground.
These electrons push away even more electrons from the Earth’s surface causing more positive charge to build up
The built-up positive charge can begin to migrate upward forming a streamer.
When the streamer and step leader meet a complete path is formed and lightning can strike!
Lightning Rods
Lightning rods are often attached to the tops of tall buildings
The rod is made of metal and then attached to a wire that is buried deep in the ground
This gives the lightning an easy path to the ground and it will avoid going through the building
The Leyden Jar
Earliest form of a battery
Charged by static electricity
Leyden Jar Demonstration