static electricity history of charged particles – 1900’s electrons(-) in shells protons(+) in...

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?