Presentation on theme: "1/31 do now An object is thrown straight upward from Earth’s surface. Graph the following for the time that elapses while it is in the air: [Neglect friction.]"— Presentation transcript:
1 1/31 do nowAn object is thrown straight upward from Earth’s surface. Graph the following for the time that elapses while it is in the air: [Neglect friction.]a-tv-td-t
2 Due today objectives Homework castle learning corrections Review packetsHomework17.1 notes due Monday 2/3Castle learning : graphsobjectivesGo over midtermGo over chapter 7 essaysGo over chapter 7 projectLab – determine power
3 2/4 do nowA cart travels with a constant nonzero acceleration along a straight line. Graph the following relationships:Acceleration vs. timeVelocity vs. timeDistance vs. time
4 Objectives Understand the basic properties of electric charge. Differentiate between conductors and insulators.Distinguish between charging by contact and charging by polarization.Homework:Castle learning: you have two days to do. If you did not finish in time, you can come post session to make up homework.
5 Atomic Structure Review Matter is made up of small structures called ATOMSWithin the NUCLEUS are two types of NUCLEONSAt the center of each atom is a NUCLEUSOrbiting the NUCLEUS are ELECTRONSELECTRONSNEGATIVE chargeOrbit nucleusPROTONSNEUTRONSPOSITIVE CHARGEDO NOT MOVEWITHIN MATTERNO CHARGE – NEUTRALDO NOT MOVEWITHIN MATTER
6 + - Charged Objects Objects are normally electrically NEUTRAL. They have the same number of protons and electronsIf an object loses electrons, itbecomesPOSITIVELY chargedIf an object gains electrons, itbecomesNEGATIVELY charged+-LACK OF ELECTRONSEXCESS ELECTRONSOnly electrons can move, protons and neutrons can not move.
7 PHYSICS - Static Electricity ExampleWhich part of an atom is most likely to be transferred as a body acquires a static electric charge?protonneutronelectronpositron7
8 PHYSICS - Static Electricity ExampleDuring a physics lab, a plastic strip was rubbed with cotton and became positively charged. The correct explanation for why the plastic strip becomes positively charged is that ...the plastic strip acquired extra protons from the cotton.the plastic strip acquired extra protons during the charging process.c. protons were created as the result of the charging process.d. the plastic strip lost electrons to the cotton during the charging process.8
9 PHYSICS - Static Electricity Charge InteractionsThe electric force is a non-contact force. Any charged object can exert this force upon other objects - both charged and uncharged objects.The nature of the electric force:Opposites attract.likes repel.9
10 The Electric Force and Newton's Third Law PHYSICS - Static ElectricityThe Electric Force and Newton's Third LawThis electric force exerted between two charged objects is a force in the same sense that friction, tension, gravity and air resistance are forces. And being a force, the same laws and principles that describe any force describe the electrical force. One of those laws was Newton's law of action-reaction. (balloons)Force of D upon C is the same in magnitude as Force of C upon D. they are action and reaction forces.Force of B upon A is the same in magnitude as Force of A upon B. they are action and reaction forces.10
11 Interaction Between Charged and Neutral Objects PHYSICS - Static ElectricityInteraction Between Charged and Neutral ObjectsAny charged object - whether positively charged or negatively charged - will have an attractive interaction with a neutral object.Positively charged objects and neutral objects attract each other;Negatively charged objects and neutral objects attract each other.Any charged object - plastic, rubber, or aluminum - will exert an attractive force upon a neutral object. And in accordance with Newton's law of action-reaction, the neutral object attracts the charged object.11
12 PHYSICS - Static Electricity Charge detectionIf two objects repel each other…one can conclude that both objects are charged and charged with the same type of charge. One could not conclude that the balloons are both positively charged or both negatively charged.If two objects attract each other…one can conclude that at least one of the objects is charged. The other object is either neutral or charged with the opposite type of charge. You cannot draw a conclusion about which one of the objects is charged or what type of charge (positive or negative) the charged object possesses.12
13 PHYSICS - Static Electricity ExampleA lightweight sphere hangs by an insulating thread. A student wishes to determine if the sphere is neutral or electrostatically charged. She has a negatively charged hard rubber rod and a positively charged glass rod. She does not touch the sphere with the rods, but runs tests by bringing them near the sphere one at a time. The student notes that the sphere is attracted to both rods. This test result shows that the charge on the sphere ispositivenegativeneutral13
14 PHYSICS - Static Electricity ExampleA negatively charged plastic comb is brought close to, but does not touch, a small piece of paper. If the comb and the paper are attracted to each other, the charge on the papermay be negative or neutralmay be positive or neutralmust be negativemust be positive14
15 Electric charge is quantized: Millikan Oil Drop Experiment: PHYSICS - Static ElectricityElectric charge is quantized: Millikan Oil Drop Experiment:The experiment determined that the charge on an object is always a multiple of a fundamental unit of charge, symbolize by e
16 Definitions charge: a fundamental property of matter measured in COULOMBS or ELEMENTARY CHARGEcharge on an object is carried by particlesElectron-1.6 x coulombs-1eProton+1.6 x coulombs+1eThe units of micro-Coulombs (1 µC = 10-6 C) or nano-Coulombs (nC = 10-9 C) are more commonly used as the unit of measurement of charge.
17 This plate is neutral – number of protons = number of electrons Charged ObjectsBecause objects can only gain or lose electrons, the only charges that are allowed are multiples of the ELEMENTARY CHARGEThis plate is neutral – number of protons = number of electronsIf the plate loses two electronsIf the plate loses one electronIf the plate loses three electronsIts charge becomes…Its charge becomes…Its charge becomes…+3 eOr+4.8 x Coulombs+2 eOr+3.2 x Coulombs+1eOr+1.6 x CoulombsThe plate has a LACK OF ELECTRONS+3 Elementary Charges+1 Elementary Charge+2 Elementary Charges
18 Example #1 An object has three excess electrons. What is its “elementary charge”?What is its charge in coulombs?-3eq = -3e x (1.6 x C)/e = x C
19 Example #2 An object has 75 protons and 65 electrons What is its “elementary charge”?What is its charge in coulombs?+10 eq = +10e x (1.6 x C)/e = +16 x C
20 Law of Conservation of Charge The total amount of charge in a closed system remains constant – charge is not created or destroyed, it only moves from one object to anotherCharge “moves” as a result of ELECTRON movement ONLY!!!
21 The TOTAL CHARGE remains the SAME!!! Example #3A metal sphere with two excess electrons touches a neutral metal sphere and then taken away.What do you predict the charge on each sphere will be after they make contact?What is the total charge on both spheres after they come in contact?-1e or -1.6 x C-2e or -3.2 x CThe TOTAL CHARGE remains the SAME!!!
22 2/6 do nowThe graph below represents the motion of a car during a 6.0-second time interval.What is the velocity during 4.0 – 6.0 s interval?What is the acceleration during 0.0 – 4.0 s interval?What is the total distance traveled by the car during this 6.0-second interval?
23 Objectives Understand the basic properties of electric charge. Differentiate between conductors and insulators.Distinguish between charging by contact and charging by polarization.Homework:Castle learning: you have two days to do. If you did not finish in time, you can come post session to make up homework.
24 Recap What is it that gives objects a charge? What are some interactions between charges?What did Miliken’s oil drop experiment determine?How is it charge measured?What is the relationship between fundamental charge and charge in coulombs.What does the Law of Conservation of Charge tell us?
25 questionA negative charged sphere is placed near a neutral sphere. Which graph represents charge distribution on the neutral sphere?--+ -- ++ -A.B.--- -- +C.D.
27 Conductive Properties of Materials NbTialloymetalssiliconwoodrubbersea waterpure waterHIGH CONDUCTIVITY LOW CONDUCTIVITYLOW RESISTIVITY HIGH RESISTIVITYGood Conductor/Poor InsulatorAllows electrons to flow freely.Good Insulator/Poor ConductorStrongly resists flow of electrons.The division of materials into the categories of conductors and insulators is a somewhat artificial division. It is more appropriate to think of materials as being placed somewhere along a continuum.
28 insulators vs. conductors charge on a conductor is quickly distributed across the entire surface of the object. Why do think this happens?Charge on an insulator will remain at the initial location of charging.The insulating cups are use to prevent charge from escaping to the surroundings as well as to provide for a convenient handle.
29 Examples of conductors and insulators Examples of conductors includemetals,aqueous solutions of saltsgraphite,waterhuman body.Examples of insulatorsplastics,Styrofoam,paper,rubber,glassdry air.
30 PHYSICS - Static Electricity Human body is a conductorAlong the continuum of conductors and insulators, one might find the human body somewhere towards the conducting side of the middle. When the body acquires a static charge it has a tendency to distribute that charge throughout the surface of the body.phet30
31 PHYSICS - Static Electricity Water is a conductorWater, being a conductor, has a tendency to gradually remove excess charge from objects. Since humidity levels tend to vary from day to day and season to season, it is expected that electrical affects (and even the success of electrostatic demonstrations) can vary from day to day.31
32 Distribution of Charge via Electron Movement PHYSICS - Static ElectricityDistribution of Charge via Electron MovementPredicting the direction that electrons would move within a conducting material is a simple application of the two fundamental rules of charge interaction. Opposites attract and likes repel.The excess negative charge distributes itself throughout the surface of the conductor. This is because electrons wish to manipulate their surroundings in an effort to reduce repulsive affects.32
33 Check your understanding PHYSICS - Static ElectricityCheck your understandingSuppose that a conducting sphere is charged positively by some method. The charge is initially deposited on the left side of the sphere. Yet because the object is conductive, the charge spreads uniformly throughout the surface of the sphere. The uniform distribution of charge is explained by the fact that ____.a. the charged atoms at the location of charge move throughout the surface of the sphereb. the excess protons move from the location of charge to the rest of the spherec. excess electrons from the rest of the sphere are attracted towards the excess protons33
34 PHYSICS - Static Electricity Charging by frictionWhen two objects are rubbed together electrons may be transferred from one object to another. One object gains electrons and the other object loses electrons, so both objects have a charge.Charging by friction results opposite charges on the two objects rubbed together.34
35 RULE #1 – ONLY ELECTRONS MOVE Charging by FrictionRub two insulators togetherELECTRONS move from one to the otherOne object becomes + the other -RULE #1 – ONLY ELECTRONS MOVE
36 PHYSICS - Static Electricity When wool is rubbed against a PVC pipe, the PVC steals electrons from the wool because it has higher electron affinity compared to wool. The PVC strip endsup with a negative charge while the woolends up with a positive chargeWhen wool is rubbed against a Nylon strip, the wool will steal electrons from the Nylon because wool has higher electron affinity than Nylon. As a result, the Nylon ends up positively charged and the wool ends up negative.36
37 PHYSICS - Static Electricity How do we know which object will gain electrons and which will lose electrons?electron affinity determines which object will gain electrons.The property of electron affinity refers to the relative amount of love that a material has for electrons. High affinity means the material has more pull to electrons.The more love of electrons a material has the more likely it is to steal electrons from the other object during charging by friction37
38 2/7 do nowWhen a neutral metal sphere is charged by contact with a positively charged glass rod, the sphereloses electronsloses protonsgains electronsgains protonsExplain you answer
39 Objectives Understand the basic properties of electric charge. Differentiate between conductors and insulators.Distinguish between charging by contact and charging by polarization.Homework:Castle learningText book - Page 633 #1-6
40 PHYSICS - Static Electricity Triboelectric seriesA triboelectric series is an ordering of substances with high affinities on top.When any two materials in the table are rubbed together, the one which is higher can be expected to pull electrons from the material which is lower.Metal can also be charged by friction40
41 Law of Conservation of Charge The total amount of charge in a closed system remains constant – charge is not created or destroyed, it only moves from one object to anotherThe frictional charging process (as well as any charging process) involves a transfer of electrons between two objects.During all charging processes, the net charge of the system is conserved.
42 Charging by Conduction PHYSICS - Static ElectricityCharging by ConductionCharging by conduction involves the contact of a charged object to a neutral object.A metal sphere with an excess of – charge is brought near to a neutral electroscope.Upon contact, e- move from the sphere to the electroscope and spread about uniformly.The metal sphere now has less excess – charge and the electroscope now has a - charge42
43 PHYSICS - Static Electricity When charging by conduction both object have the same type of charge when separated.If A negatively charged object touches a neutral object the neutral object gains electrons and becomes negatively charged as well.If a positively charged object touches a neutral object then the neutral object loses electrons and when separated it is positively charged as well.To charge by conduction successfully your charged and neutral object must be conductors!43
44 Law of Conservation of Charge PHYSICS - Static ElectricityLaw of Conservation of ChargeIn a closed system, charge is always conserved. The total amount of charge among the objects is the same before the charging process starts as it is after the process ends.44
45 PHYSICS - Static Electricity exampleTwo metal spheres having charges of +4.0 × 10-6 coulomb and +2.0 × 10-5 coulomb, respectively, are brought into contact and then separated. After separation, the charge on each sphere is8.0 × C8.0 × 10-6 C2.1 × 10-6 C1.2 × 10-5 C45
46 Castle learning questions A joule is equivalent to aN•mN•sN/mN/sKg∙m2/s2There could be more than one answer.
47 Polarization - Why a charged object attract neutral object In an atom, the protons are tightly bound in a nucleus and incapable of movement. In conducting objects, electrons are so loosely bound that they may be induced into moving from one portion of the object to another portion of the object.By placing a charged object near a neutral conducting object you can create electron movement.
48 PHYSICS - Static Electricity No electrons have been added to or subtracted from the can yet there is a charge at either end of the can; overall the can is electrically neutral. This arrangement of charge is called polarization.48
49 PHYSICS - Static Electricity Polarization is the process of separating opposite charges within an object.The polarization process always involves the use of a charged object to induce electron movement or electron rearrangement.By inducing the movement of electrons within an object, one side of the object is left with an excess of positive charge and the other side of the object is left with an excess of negative charge. Charge becomes separated into opposites.Polarization is not charging – the total charge in a polarized object is still zero just like before.49
50 A surface charge can be induced on insulators by polarization PHYSICS - Static ElectricityA surface charge can be induced on insulators by polarizationIn an insulator, electrons merely redistribute themselves within the atom or molecules nearest the outer surface of the object.50
52 Polarization is Not Charging PHYSICS - Static ElectricityPolarization is Not ChargingWhen an object becomes polarized, there is simply a redistribution of the centers of positive and negative charges within the object.While there is a separation of charge, there is NOT an imbalance of charge. When neutral objects become polarized, they are still neutral objects.52
53 PHYSICS - Static Electricity exampleAn inflated balloon which has been rubbed against a person's hair is touched to a neutral wall and remains attracted to it. Which diagram best represents the charge distribution on the balloon and the wall?abcd53
54 exampleThe diagram below shows three neutral metal spheres, x, y, and z, in contact and on insulating stands. Which diagram best represents the charge distribution on the spheres when a positively charged rod is brought near sphere x, but does not touch it?CDAB
55 PHYSICS - Static Electricity The ElectroscopeAn electroscope is a device which is capable of detecting the presence of a charged object through polarization.55
56 Polarization of an electroscope PHYSICS - Static ElectricityPolarization of an electroscope56
57 RULE #2 – GROUNDING MAKES AN Since the Earth is very large it can neutralize:negative objects by ABSORBING electronspositive objects by RELEASING electrons-+-+--+-+RULE #2 – GROUNDING MAKES ANOBJECT NEUTRAL---Grounding Symbol:-
58 PHYSICS - Static Electricity Charging by Inductioncharging by induction method is to charge an object without actually touching the charged object.Charging by induction requires conductor, polarization, and grounding.58
59 Charging by induction using two conductors PHYSICS - Static ElectricityCharging by induction using two conductors59
60 Charging a single sphere by induction PHYSICS - Static ElectricityCharging a single sphere by induction60
61 The Importance of a Ground in Induction Charging PHYSICS - Static ElectricityThe Importance of a Ground in Induction ChargingIn the charging by induction cases, charge is never transferred from the charged object to the neutral object… They do not touch! The charged object causes the neutral object to become polarized.The neutral object got charged through a ground.A ground can serve as a supplier or receiver of electrons.61
63 PHYSICS - Static Electricity Grounding is also a way of uncharging an object.63
64 The Need for a Conducting Pathway PHYSICS - Static ElectricityThe Need for a Conducting PathwayAny object can be grounded provided that the charged atoms of that object have a conducting pathway between the atoms and the ground.Electrons will travel along that pathway.64
65 Charging an electroscope by induction PHYSICS - Static ElectricityCharging an electroscope by inductionBring a charged object near the electroscopeThe electroscope is being polarized.Touch the part of the electroscope that is away from the charged object.Remove your hand.Remove the charged object.65
66 fundamental principles regarding induction charging PHYSICS - Static Electricityfundamental principles regarding induction chargingThe charged object is never touched to the object being charged by induction.The charged object does not transfer electrons to or receive electrons from the object being charged. The charged object serves to polarize the object being charged.The object being charged is touched by a ground; electrons are transferred between the ground and the object being charged (either into the object or out of it).The object being charged ultimately receives a charge that is opposite that of the charged object which is used to polarize it.66
67 PHYSICS - Static Electricity exampleA charged body may cause the temporary redistribution of charge on another body without coming in contact with it. This process is calledconductionpotentialCharging by frictioninduction67
69 PHYSICS - Static Electricity ExampleAn object can not have a charge of3.2 × C4.5 × C8.0 × C9.6 × CWhat is the smallest electric charge that can be put on an object?9.11 × C1.60 × C9.00 × 109 C6.25 × 1018 C69
70 Example – change electrons to Coulomb What is the net charge of an object possessing an excess of 6.0 x 106 electrons?Since there are 1.6 · Coulomb in 1 electron, you can multiply the number of electrons by 1.6 · Coulomb to find the result.(6.0 · 106 e)(1.60 · C/e) = 9.6 x C
71 Example – change Coulomb to electrons A metal sphere has a net negative charge of 1.1 x 10-7 coulomb. How many more electrons than protons are on the sphere?Since there are 6.25 · 1018 electrons in 1 Coulomb, you can multiply the number of Coulomb by 6.25 x 1018 electrons to the result. x = x 1011 e(1.1 · 10-7 C)(6.25 · 1018 e/C) = x 1011 e
72 exampleIf an object possessing an excess of 6.0 × 106 electrons, what is its charge in Coulombs?Which quantity of excess electric charge could be found on an object?0.25 elementary charges5.25 × C6.40 × C1.60 elementary charges
73 7.1 Characteristics of uniform circular motion What is uniform circular motion?Describe the magnitude and the direction of velocity of a uniform circular motion.Describe the magnitude and the direction of acceleration of a uniform circular motion.Describe the magnitude and the direction of net force of a uniform circular motion.What does centripetal mean?Why is force required when an object moves in a circle?How is centripetal force related to mass, velocity and radius of the object moving in a uniform circular path? Give examples to show your understanding.
74 7.3 The law of universal gravitation What is inverse squared relationship? Give examples to show your understanding.What does “universal” in the law of universal gravitation mean?What is gravity?Write the equation of universal gravitation and indicate each symbol in the equation mean. Draw a picture to show your understanding.How is gravitational force related to masses of each object and how is it related to the distance from the center of each mass? Give examples to show your understanding.How is value g related to the distance from the center of Earth?Draw a picture to illustrate that gravity is a field force.
76 1/30 do now 1) A metallic sphere gains 500 electrons. a. Determine the amount of ‘elementary charge’ that is now on the sphere. Be sure to indicate positive or negative!b. Calculate the charge on the sphere in coulombs.
78 objectives Know: Definition of insulator, conductor Charge is transferred in solids by electron movement only.Understand:How charge is transferred by contact and inductionHow surface charge can be induced on insulators by polarization.Be able to:Explain how charged object attract neutral objects