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 1.60x C Protons carry the smallest possible negative charge. The charge on one proton +e is 1.60x C

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 19-1 Triboelectric Charging MaterialRelative 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 19-5 Electrical 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

-100 A) Both 0 B) Both –10 C) Both –5 D) Both +5 IC

+100 IC In which direction do the electrons move A) Left B) Right C) Neither D) Both

IC

IC Which sphere is more negative and in which direction do the electrons flow? A)right, rightB) right, left C) left, rightD) left, left

IC IC Final Charge after sharing is A)–24B) –12 C) –2D) +2

-10 0 Sharing when objects are not the same size.

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 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 Generator Van 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?