Transcript UNIT III Electricity

Science 9
Electricity
Static Electric Charge
Sci300- Gillis
Static Electric Charge (9-2)

Static electric charge
A charge on a
substance that stays in
the same place
+
-
Examples of Static Charge
Lightning(9-10)

http://www.youtube.com/watch?v=gKPwkau0Dh0
&feature=related
http://www.youtube.com/watch?v=HLcFHo2HR7I
&feature=related

Static cling-
Examples of Static Charge

Static shock-
Producing Static Electricity

Charge by Friction- (9-3)

Electric charge is transferred by rubbing object
together
Producing Static Electricity
We know which
object will cause
which charge when
caused by friction
using the
Electrostatic Series
(9-3)
(Items above become negatives)
 Rubber
 Ebonite
 Polyethylene
 cotton
 silk
 wool
 glass
 acetate
 fur/hair
(Items below become positives)
Producing Static Electricity

Charge by conduction (contact)- (9-5)

Charge is transferred by touching a charged
object to an uncharged object
http://www.shep.net/resources/curricular/physi
cs/P30/Unit2/electroscope.swf
Producing Static Electricity

Charge by induction- (9-8)

Neutral object becomes charged when a
charged object is brought near it.

Induced charge can become more permanent if a
ground wire is attached to it.
http://www.shep.net/resources/curricular/physi
cs/P30/Unit2/electroscope.swf
Laws of Electric Charge (9-2)


Unlike charges attract one another
Like charges repel one another
Removing Static Electricity (9-7)

Discharge (neutralize)
When excess electric charge is removed from
an object.
Discharge can be quick and explosive (lightning)
 Discharge can be unnoticed (fabric softener sheet)

http://www.youtube.com/watch?v=R7cgazVkhTk&fe
ature=related
Removing Static Electricity

Grounding

Connecting the object to the earth


The charge is shared with the entire earth
Discharge at a point

Objects made into a point have electrons
pushed off the end.
Detecting Static Charge

Electroscope -a device used to detect the
presence of charge. (9-4)

usually constructed with a metal plate or
sphere at the top of a metal post with thin foil
leaves hanging from the bottom of the post
http://www.regentsprep.org/Regents/physics/p
hys03/aeleclab/nerscope.htm
Dangers of Static Electricity
Cause fires
http://www.metacafe.com/watch/862578/static_el
ectricity_causes_fire_at_gas_station/
 Can wreck electronics (need grounding wire)
 Can hurt (shock) or cause death (10-9)
http://www.youtube.com/watch?v=CpxKEGdfDxI&
feature=related

Uses of Static Electricity (9-8)

Electrostatic air cleaners


Removes dust and other particles by the
attraction of unlike charges
Electrostatic spray painting
The paint and the object to be painted are
given opposite charges
http://video.google.com/videoplay?docid=860069260229630847

Uses of Static Electricity (9-11)

Fabric softener sheets



Allows electric charge to move in between
clothes instead of building up.
Photocopiers
Cell phones and car radios