1. Chapter 20 Notes Static Electricity

2. Ben Franklin’s experiment in 1752 Electrostatics-The study of electrical charges that can be collected and held in one place, in other words, they are AT REST

3. Something about ATOMS Every atom has a positively charged nucleus surrounded by negatively charged electrons All electrons are identical (same mass and charge) Nucleus=protons and neutrons Atoms usually have an equal number of protons and electrons

4. Charge Electrons are negatively charged Protons are positively charged The attracting and repelling is due to something called charge LIKE CHARGES REPEL OPPOSITE CHARGES ATTRACT

5. Insulators Materials through which charges will not move easily Examples-glass, dry wood, plastics, cloth, dry air

6. Conductors Materials, such as metals, that allow charges to move about easily. Charge spreads very quickly over the entire object Examples-door knob, desk, lightening rod

7. Why are metals good conductors? Because at least one electron on each atom of the metal can be removed easily; they move freely throughout the entire piece of metal Most of the time, the materials involved in Static Electricity are nonconductors of electricity

8. Conservation of Charge Individual charges are never created nor destroyed The combined total charge of 2 interacting objects remains the same

9. Things to Remember!! 2 Kinds of Electrical Charges- Positive & Negative Charges exert force on other charges over a distance The force is stronger when the charges are closer together Like charges repel, Opposite charges attract

10. How do we Charge Object? Conduction Charging a neutral object by touching it with a charged object

11. Induction Charging a neutral object by bringing it close to a charged object, causing a separation of charges, then removing the object to be charged, trapping equal but opposite charges

12. Coulomb’s Law Says that the magnitude of a force between 2 charges varies directly with the magnitude of the charges and inversely with the square of the distance of the charges F=K(qq/d 2 ) K is a constant K=9.0x10 9 Nm 2 /coul 2

13. Electric Potential Energy Bodies with diff. concentrations of electrons have a difference in potential between them. This means that the 2 bodies are a source of potential energy. The difference in potential is measured in Volts (v)

14. Electrons flow from areas of higher conc. to areas of lower conc. An electron flow takes place if 2 bodies have a difference in potential and are connected by a conductor. This flow is called an electric current.

15. The way to maintain a current is to maintain a charge on the 2 bodies that are at diff. potentials. To maintain the potential, some devices must pump the electrons back to the body with higher concentrations as soon as they get to the lower concentration. These are called Voltaic Cells-Batteries.