Vocabulary Quiz-Thursday

Charging by Friction and Contact

Charging by Friction and Contact

• When electrons are transferred by one material rubbing against the other

Van de Graaff Generator

• Invented by American physicist Robert Van de Graaff, 1929

Why this happens

Friction

• Charges can separate from one another in clouds, due to friction

1. Cloud to ground2. Cloud to cloud or Intracloud

The charged regions within the atmosphere temporarily equalize themselves through a lightning

flash

Cloud-to-ground lightning occurs when negative chargesaccumulate in the lower portions of the cloud.

Positive charges are attracted to a relatively small area inthe ground directly beneath the cloud establishing a large

voltage difference between the ground and the cloud base.

About 80 percent of all lightning is cloud-to-cloud lightning, or sheet lightning (b/c it lights up the sky with a sheet of light),

which occurs when the voltage gradientwithin a cloud, or between clouds, overcomes the electrical

resistance of the air. The result is a large and powerfulspark that partially equalizes the charge separation.

Sheet Lightning

Heat Lightning

Lightning from a thunderstorm that is too far away to be heard.

Forked Lightning-

• Has branching in its paths

A bizarre type of electrification called ball lightningappears as a round, glowing mass of electrified air,

up to the size of a basketball, that seems to roll throughthe air or along a surface for 15 seconds or so

before either dissipating or exploding.

Seen escorting bomber planes in World War II just off their wingtips. Pilots referred to it as “foo fighters” as they initially were thought to be enemy planes.

Ball Lightning

Fulgariteshttp://www.madebymeg.net/blog/sea-glass-made-from-lightning/

Hollywood Reality• A hollow fragile rock

The benefit of lightning

• Heat and pressure from lightning also breaks down the nitrogen in our air to a useful form.

• The nitrogen acts as a natural fertilizer.

• Most common cause of death is cardiac arrest– In humans 70% of victims

survive because CPR was given in time

– Animals have a nearly 100% mortality rate because CPR is unable to be given to them

• Most common visual injury is burns

Lightning’s affect on Humans and Animals

Induction

• The charging of an object without direct contact

Induction

Grounding

It acts as overvoltage protection in the case of lightning or a power surge. The extra electrons go into the earth.