2. Charge A proton, electron, or an excess of protons or electrons. + - Proton Electron A positive charge A negative charge + + ++ + + + + - - - - - - - A Positively charged body A Negatively charged body + _ - - - - Representation of a positively charged body Representation of a negatively charged body

3. Charge Fundamental property of matter Measured in a unit called Coulomb, abbreviated C. The Coulomb was named after a French Physicist Charles Augustin de Coulomb (1736-1806). There are 15 C of charge in a typical lightning bolt. Charge is denoted by the letter q. (Example q=15 C for a typical lightning bolt.) Charge is analogous to mass in the mechanical system. Charge force law: Like charges repel, unlike charges attract.

4. Determination of Charge Value (The Milikan Oil Drop Experiment) Performed by Robert Milikan in 1909. Received Nobel Prize for experiment

5. Milikan’s Method of Calculation + FeFe W F e = electrical force on the charged oil drop W= weight charged of oil drop F e =qEW=mg Fe=W when the charged oil drop was suspended by the electric field. qE=mg  q=mg/E

6. proton: fundamental positive charge = q p = +1.6 x 10 -19 C electron: fundamental negative charge = q e = -1.6 x10 -19 C - + Charge The number of charges in one Coulomb of charge: +1.0 C = 6.25 x 10 18 protons - 1.0 C =6.25 x 10 18 electrons Neutron: zero charge How many and what type of charge are in - 5.0 C? How much charge are in one mole of protons? 3.1 x 10 19 electrons 9.6x10 4 C Exact relationship: 1.602x10 -19 C = charge of a single proton or electrons.

8. Point charge - a single charge or a quantity of charges within an extremely small region of space. + + + + + + + + + + + + + + + + +

9. - + + + + - - - All three bodies shown directly below are neutral (0 C). Since the conductor is made of protons, electrons, and neutrons charge is still available, but they are balanced. + +1 q = +1.6 x10 -19 C - - - - - + + -3 q = -4.8 x 10 -19 C 0 q = 0 C There is excess charge on the first two conductors, the third has zero charge.

10. Material Conductivity Classification Conductor - a material that transfers charge easily. Ex: metals. –Charges on conductors spread throughout the conductors. Insulator - a material that does not transfer charge easily. Ex: rubber, glass, wood. –Charges on insulators stay stationary on the insulator. Semiconductor – a material that transfers charge at a level between a conductor and insulator. Ex: Silicon

11. Polarization Separation of charge without a transfer. - - - - - Before polarization During polarization - - - - - + After polarization - - - - - - - - - - + - + + + + + + + + + + + + - -- - - - - - - + Not a form of charging Since charges are not transferred. Polarization of a conductor

12. Polarization - - - - - Before polarization During polarization - - - - - - After polarization - - - - - + - Polarization of a non-conductors Not a form of charging Since charges are not transferred.

13. Methods of charging Charging by Friction – the transfer of charge by the rubbing of objects. Charging – the process of transferring electrons or protons. The electrons are extracted from one object and transferred to the other by rubbing them together. - - - + + + -3 +3 Before charging by friction After charging by friction Since charge is conserved, the same number electrons gained by one object, is the same number of electrons lost by the other object. Negatively charge Positively Charge

14. Charging by Conduction Charging by Conduction – transfer of charge due to contact between objects - - - Before charging During Charging - - - - - - After Charging - - - - - The sphere is now negatively charged. - or

15. Charging by Induction Ground – an alternate path charges can travel through Charging by induction – charging by forcing charges out of a grounded object. The object with the ground now has the opposite charge of the object causing the induction. - - - - - Before charging During charging - - - - - + + + + + - - - Ground wire to another surface. After charging - - - - - + Net negative charge Net positive charge