Aim: How do charges flow into and out of objects? Do Now: Quiz HW: Problem Set

How do objects gain charge? Positive protons sit inside an atom and are unmovable! Electrons orbit the nucleus and can be gained or lost. Ionization: Process of gaining a positive or negative charge. ONLY ELECTRONS MOVE, NEVER PROTONS!!!

ATOM REVIEW Matter is made up of small structures called ATOMS Within the NUCLEUS are two types of NUCLEONS At the center of each atom is a NUCLEUS Orbiting the NUCLEUS are ELECTRONS ELECTRONS NEGATIVE charge Orbit nucleus PROTONS NEUTRONS POSITIVE charge DO NOT MOVE under “normal conditions” Uncharged – NEUTRAL DO NOT MOVE under “normal conditions”

Charge Demos Ripping tape Attracting paper Why does neutral paper attract? Sketchy Taser Electroscope Balloons

Charges Laws + + - - + - Like charges repel (move away) (+ +) (- -) Opposite charges attract (+ -) - - + -

Demonstration  Why does a charged object attract a neutral object?   - + +  + -     +  Ex. Rods and cloth

+ - Charged Objects Normally, objects are electrically NEUTRAL. They have even numbers of protons and electrons If an object LOSES electrons, it becomes POSITIVELY charged If an object GAINS electrons, it becomes NEGATIVELY charged + - Demonstrate with pith balls/packing peanuts/van de graff/sketchy tool LACK OF ELECTRONS EXCESS ELECTRONS

Note: “q” is the variable letter The Coulomb The basic unit of charge is the Coulomb 1e=1.6x10-19C 1C=6.25x1018e (elementary charges) Proton: Charge= +1.6x10-19C=+1e Electron: Charge= -1.6x10-19C=+1e Note: “q” is the variable letter used for CHARGE What is the charge if I give it one electron? 2? 3? What if I take away one electron? What do you notice about the increments? Difference between conversions, 1C is a ton of elementary charges! 1e is a small coulomb charge!

Charged Objects Objects can only gain or lose multiples of ELEMENTARY CHARGE This plate is neutral , so the # of PROTONS = # of ELECTRONS Number of Electrons Lost Plate’s Elementary Charge Plate’s Coulomb Charge 1 +1e +1.6x10-19 C 2 +2e +3.2x10-19 C 3 +3e +4.8x10-19 C The plate LACKS ELECTRONS

How do we describe static charge? Electrons build up in one object (due to friction – rubbing) and quickly jump to another object when touched causing an electric spark or shock.

How is a lightning bolt produced? Clouds become NEGATIVE by rubbing against each other (friction) and picking up electrons. When this electron build up is large you see lightning

Electron and Coulomb Conversions 1) Determine the net charge on Peter after he rubs his feetsie pajamas on a rug and gains an excess of 2.5x104 electrons. 2) A metal sphere has net negative charge of -4.0x10-8 Coulombs. Determine the number of excess electrons.

SUMMARY Describe the characteristics of a… Variable letter for charge? Proton Neutron Electron Variable letter for charge? Unit(s) for charge? 1 elementary charge = ? How do objects gain/lose charge? Describe the Law of Conservation of Charge

Envelope Activity Using the envelope at your table, describe the flow of charge for the following situations.

Describe the flow of charge A balloon is rubbed on Rachel’s head. The balloon becomes negatively charged. A glass rod is rubbed with silk cloth. The rod becomes positively charged. Lightning strikes the empire state building.

Inductors and Conductors Very loosely bound valence electrons. Charges move very easily. What are some examples? Metals INDUCTORS Very tightly held electrons. Charges do not move through very easily. What are some examples? Plastic

Review How does an object gain a charge? I have 2 metal spheres. They have respected charges of 2x10-8C and -6x10-8C. What is the charge on each sphere after they are all brought together and then separated? What kind of material is the metal sphere? What is the charge on each sphere in terms of elementary charges? Electrons are gained or lost. Protons can NOT move. The average between the two spheres is the resulting net charge on each.

Induction Animation Induction Animation Think about the flow of electrons!