1. ELECTROSTATICS Electrostatics - the study of electricity at rest.

2. ELECTROSTATICS Electrical Forces arise from particles in atoms -can be either repulsive or attractive Like charges repel. -protons repel protons (  + +  ) -electrons repel electrons (  - -  ) Unlike charges attract. -protons and electrons attract each other (+   -)

3. ELECTROSTATICS

4. Charge – a property that is attributed with attractive or repulsive behavior In the atom, by convention (general agreement), electrons are assigned a negative charge (-) protons are assigned a positive charge (+), and neutrons are neutral (0).

5. ELECTROSTATICS Facts about Atoms: -positively charged nucleus surrounded by negatively charged electrons -electrons are identical (same mass and same amount of negative charge) -nucleus is made of positively charged protons and neutral neutrons -all protons are identical (same mass and same amount of positive charge) -all neutrons are identical (same mass)

6. ELECTROSTATICS Atoms have the same number of protons and electrons. # of protons = # of electrons Neutral atom has a net charge of zero. Atom with extra electrons has a net negative charge. negative ion Atom with less electrons has a net positive charge. positive ion Only electrons can be lost or gained - not protons or neutrons.

7. Atoms and Ions

8. UNIT OF CHARGE Coulomb - SI unit of charge - abbreviated C 1 Coulomb is the charge on 6.24 x 10 18 electrons The charge on 1 electron is (1/6.24 x 10 18 ) = -1.6 x 10 -19 C

9. COULOMB’S LAW The electrical force between charged particles is directly related to the charge of each particle and inversely related to the square of the distance between the particles. F = k q 1 q 2 ---------- d 2 k = 9.0 x 10 9 N. m 2 C 2

10. COMPARE and CONTRAST NEWTON’S LAW OF GRAVITATION F = G m 1 m 2 G = 6.7 x 10 -11 N. m 2 d 2 kg 2 COULOMB’S LAW F = k q 1 q 2 k = 9.0 x 10 9 N. m 2 d 2 C 2

11. COMPARE and CONTRAST Newton’sCoulomb’s GravitationElectrical Similarities 1. 1. 2. 2. Differences 1. 2.

12. COMPARE and CONTRAST Newton’sCoulomb’s GravitationElectrical Similarities 1. Product of masses1. Product of charges 2. Inverse square law2. Inverse square law Differences 1. Very small constant1. Very large constant (very small force) (very large force) 2. Attractive force only2. Attractive and repulsive

13. INSULATORS and CONDUCTORS Conductors - materials that allow electric charge to move easily - “loose” electrons Examples: Insulators - materials that do not allow electric charge to move easily Examples:

14. CHARGING MATERIALS FRICTION - this is the process of adding or taking away electrons by moving objects across each other.

15. CHARGING MATERIALS CONDUCTION OR CONTACT - the process of giving a charge to an object by touching it with another charged object.

16. CHARGING MATERIALS INDUCTION - the process of charging an object by bringing another charged object near but not touching the object.

17. CHARGE POLARIZATION An object can be electrically polarized when one side of the object is more negative (or positive) than the other side of the object.