(2.22P-2.28P) Electric Charge
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11 Terms
What is a conductor? Give some examples.
A material that allows charge to flow through it easily: usually metals, copper, iron
Why are metals such good conductors?
They have free, charged particles.
(sea of delocalised electrons)
What is an insulator? Give examples.
A material that does not easily allow charge to flow through: plastic, rubber
What is a static charge?
Charge that build up in one place and is not free to move.
How can static charge build up?
often friction-
2 insulating materials rub against each other
exchanging elections
therefore gaining an electrostatic charge
How can a charged conductor be discharged?
Connecting it to earth with a metal strap so electrons can safely flow to/from it
Describe the behaviours of charged objects.
like charges repel, opposite charges attract
Experiment to investigate how insulating materials can be charged by friction.
when a polythene rod is rubbed with cloth, electrons move from rod to cloth.
when an acetate rod is rubber with cloth, electrons move from cloth to rod.
This can be tested by suspending a rod with a known charge and bringing the tested rod close to it. By seeing whether it is repelled or attracted, you can work out whether it has become charged.
Why can static electricity present a fire risk?
electric charge builds on an isolated object.
as does voltage between the object and the ground
if large enough, electrons can jump the gap- spark!
this can be a fire risk.
Why can static electricity be dangerous? (fuel)
as fuel (liquid insulator) flows out of a filler pipe, static can build up.
if a spark forms, fuel could ignite.
so, have earthing straps between the tank and the pipe + have a pathway for buildup to be conducted away.
How do photocopiers use static electricity?
image projected onto positive plate
plate loses charge in light areas, keeps positive charge in dark areas
negative black powder applied to plate and sticks to positive part
transferred to new blank paper
heated to make powder stick