1. Electrostatics and Electric Fields Parts of an atom Parts of an atom Nucleus (protons, neutrons) Electrons Protons are positive (+) Electrons are negative (-) The force that holds atoms together is the strong nuclear force.

2.  There are four fundamental forces in nature. 1. Gravitational 2. Electromagnetic 3. Strong Nuclear 4. Weak Nuclear  Many items in nature are conserved- this means they cannot be destroyed. Mass, energy, momentum, and charge.

3.  Charge (q or Q) measured in a unit called Coulombs (C).  The charge on an electron or proton is the same, 1.602 E-19 C.  Charges of like signs repel.  Charges of opposite signs attract.  Neutral atoms have equal numbers of protons and electrons.  Electrons are able to move from one place to another, protons are not.

4.  Coulomb’s Law- The Force that exists between two charged particles depends on the amount of charge on each and the distance squared between them.  F e = kq 1 q 2 / r 2 k = 9 E9 Nm 2 /C 2  F ~ qq If charges change, force changes the same way.  F~ 1/r 2 If distance increases, force decreases. Ex: if r doubles, F=1/4 original force.

5. Charge Transfer  Charges can be transferred 3 ways  Conduction (Friction and Contact)  Induction (nearness of charged objects)  Polarization (temporary realignment)

6.  Conductors- allow electrons to move freely, usually charge will sit on the surface.  Insulators- charges are more tightly bound. Even charge distribution.  Semiconductors- usually mixed with an alloy to turn an insulator into a conductor.  Superconductors- very low resistance to the flow of charge at certain temps. Can conduct electricity without heating.

7. Electric Fields  Electric Field- a region in space where an electric force can be detected.  E = F e /q E = kq/r 2 Unit: N/C  Electric Field and Electrostatic Force are vectors, the direction matters!  Electric Field lines are drawn from a positive toward a negative. + -