1. Electric Charge and Electric Force

2. What is an Electric Charge? Protons have positive (+) electric charge Electrons have negative (-) electric charge.

3. What is an Electric Charge? Atoms become charged by gaining or losing electrons. Static electricity —the accumulation of excess electric charges on an object.

4. Calculating Charge Electric charge was quantified by Robert Millikan in 1909. Battery On ---- ++++ Atomizer - charge

5. Millikan discovered that all the oil droplets had a charge of 1.60 x 10 -19 Coulombs (C) or multiples of this charge. Electron = -1.60 x 10 -19 C Proton = +1.60 x 10 -19 C Neutron = 0 C Calculating Charge

6. Charged Objects Electrically charged objects obey the following rules: - Law of conservation of charge- charges may be transferred, but they cannot be created or destroyed. –Opposite charges attract, and like charges repel. - + -

7. Charged objects How are these charges able to move towards or away from each other?How are these charges able to move towards or away from each other? Electrical force: force that is exerted by + and – charges on one another. Like gravity, electrical force is a “field force” – force without physical contactLike gravity, electrical force is a “field force” – force without physical contact Objects placed close together will experience a greater force – Coulomb’s LawObjects placed close together will experience a greater force – Coulomb’s Law

8. Charged objects Coulomb’s Law F electric = K c [(q 1 q 2 )/r²] Kc = Coulomb constant = 8.99 x 10 9 N m²/C² q = charge r = distance between the two charges

9. Transferring Electric Charge Charging by contact –The process of transferring charge by touching or rubbing Example: static electricity from your feet rubbing the carpet –Works best on non-conductive materials.

10. Transferring Electric Charge Charging by induction –The rearrangement of electrons on a neutral object caused by a nearby charged object. Occurs in conductors! + - + - + - + - ---- Charged Object Conductor

11. Transferring Electric Charge Charging by Polarization –Same concept as induction, but in insulators! –The rearrangement of electrons on a neutral object caused by a nearby charged object. ---- Charged Object ---- Insulator = + = - = neutral

12. Transferring Electric Charge Static discharge –A transfer of charge through the air between two objects because of a buildup of static electricity. Example: lightning Grounding—using a conductor to direct an electric charge into the ground.