Everyday Electricity

11
Everyday Electricity February 26th, 2009

Transcript of Everyday Electricity

Page 1: Everyday  Electricity

Everyday Electricity

February 26th, 2009

Page 2: Everyday  Electricity

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)

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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

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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)

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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

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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

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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!

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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

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The Leyden Jar

Earliest form of a battery

Charged by static electricity

Leyden Jar Demonstration