static electricity history of charged particles – 1900’s electrons(-) in shells protons(+) in...
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Static Electricity
• History of charged particles – 1900’s
• Electrons(-) in shells• Protons(+) in nucleus• Neutrons(0) in nucleus
Static Electricity• The SI unit for electric charge is the
coulomb: C• Electrons carry the smallest possible
negative charge. The charge on one electron -e is 1.60x10-19C
• Protons carry the smallest possible negative charge. The charge on one proton +e is 1.60x10-19C
Static Electricity• An object may be charged by rubbing it
by another object. Only electrons may be lost or gained by a rubbed object.
• If the atom loses electrons, it will become____
• If the atom gains electrons, it will become ____
Static Electricity
Protons are never transferred!!!
Charges are never created nor destroyed. =
Law of Conservation of Charge
Rubbing to lose/gain e-–Rub a glass rod with silk
– the silk gains -e and the glass loses -e –Rub a rubber rod with fur
– the fur loses -e and the rod gains -e –They will be oppositely charged and
therefore attract each other.
Table 19-1Triboelectric Charging
Material Relative charging with rubbing
Rabbit fur + + + + + +
Glass + + + + +
Human hair + + + +
Nylon + + +
Silk + +
Paper +
Cotton -
Wood - -
Amber - - -
Rubber - - - -
PVC - - - - -
Teflon - - - - - -
Charging by Contact
• Conductors – electrons are easily transferred
• (ex: metals – Ag, Au, Cu)• Insulators – electrons do not move easily
from one location to another – (ex: wood, plastic, air)
Figure 19-5Electrical Polarization
Charging by Contact
Conduction
• If two objects touch, they will have the same charge and REPEL (unless they were neutral)
• Like charges REPEL• Demo- Rub
balloon in your hair!
• The Law of Electrostatics
• LIKES REPEL
• OPPOSITES ATTRACT
Demos
• 1. Paper & Golf Tube• 2. Golf Tube & 2” x 4” x 8’• 3. Balloon on the Wall
Conduction is just like sharing
• To charge an object by touching it with another charged object. The second object shares the charge and is always the same charge as the first object.
• Examples of sharing
Charging by Conduction
-10 0
A) Both 0 B) Both –10
C) Both –5 D) Both +5
IC
-10 0
-5 -5
+10 0
IC
IC
In which direction do the electrons move
A) Left B) Right C) Neither D) Both
+10 0
+ 5 + 5
-10 -14
IC
-10 -14
-12 -12
+10 +14
IC
IC
Which sphere is more negative and in which direction do the electrons flow?
A) right, right B) right, left
C) left, right D) left, left
+10 +14
+12 +12
+10 -14
IC
IC Final Charge after sharing is
A)–24 B) –12
C) –2 D) +2
+10 -14
-2 -2
-10
0
Sharing when objects are not the same size.
0
-10
-
--
--
-
-
-
-
-Sharing ?
Grounding
• Sharing charge between an extremely large object, like the EARTH, and a small object is called grounding. All the charge winds up in the earth and no charge is on the small object.
Induction
• Charging by induction–Case #1 - bring a negative object near–Case #2 - bring a positive object near
Charging by Induction
Charging by Induction
Charging by Induction
Charging by Induction
Charging by Induction t = 5 sec
Charging by Induction
Balloons on the Ceiling
• Why do balloons stick to the ceiling when rubbed on your hair?
Balloon on the Ceiling or Wall
Using a Van de Graaff GeneratorVan de Graaff in action
Wild Hair
Demos with the VDG
• 1. A hair raising experience• 2. Packing pellets• 3. Ribbon• 4. Silver ball
Lightning
• Where is the safest place in a lightning storm?
Find the BOLT?